http://toplegendarycars.blogspot.com/2012/05/plymouth-barracuda.html
Although Plymouth already had a performance car in the GTX, designers decided to go back to the drawing board and reincarnate the original muscle car concept. Plymouth wanted a car able to run 14-second times in the quarter mile (402 m) and sell for less than US$3000. Both goals were met, and the low-cost muscle car hit the street. The success of the Road Runner would far outpace the upscale and lower volume GTX, with which it was often confused.
Paying $50,000 to Warner Brothers to use the name and likeness of their Road Runner cartoon character (as well as a "beep, beep" horn, which Plymouth paid $10,000 to develop), and using the Chrysler B platform as a base (the same as the Belvedere, Satellite, and GTX), Plymouth set out to build a back-to-basics muscle car. Everything essential to performance and handling was beefed-up and improved; everything nonessential was left out. The interior was spartan with a basic cloth-and-vinyl bench seat, lacking even carpets in early models, and few options were available - just the basics such as power steering and front disc brakes, AM radio, air conditioning (except with the 426 Hemi) and automatic transmission. A floor-mounted shifter (for the four-speed) featured only a rubber boot and no console so that a bench seat could be used. The earliest of the 1968 models were available only as 2-door pillared coupes (with a B-pillar between the front and rear windows), but later in the model year a 2-door "hardtop" model (sans pillar) was offered.
The Road Runner of 1968-1970 was based on the Belvedere, while the GTX was based on the Satellite, a car with higher level trim and slight differences in the grilles and taillights. Plymouth dealers gave away this promotional windbreaker in 1970. The "heart with an arrowhead at bottom" design was part of Plymouth's ad campaign that year. The Road Runner is holding a helmet with the same symbol on it. The standard engine was an exclusive-to-the-Road Runner 383 CID (6.3 L) Roadrunner V8 rated at 335 bhp (250 kW) and 425 lb·ft (576 N·m) of torque. Its extra 5 hp (4 kW) rating was the result of using the radical cam from the 440 Super Commando and a .25 raise in compression to 10.5:1 (vs. 10.25:1 with the 330 hp (246 kW) 383). When air conditioning was ordered, the cars received the 330 hp (246 kW) version, as the radical cam specs of the 335 bhp (250 kW) version didn't create enough vacuum to accommodate a/c; and there were concerns of overrevving which would grenade the RV-2 York compressor. For an extra $714, Plymouth would install a 426 CID Hemi rated at 425 bhp (317 kW) and 490 lb·ft (664 N·m) of torque. Combined with low weight, the 6-passenger Road Runner could run the 1/4 mile in 13.5 seconds at 105 mph (169 km/h). It would prove to be one of the best engines of the muscle car era, and the Road Runner one of the best platforms to utilize it.
The standard equipment transmission was a four-speed manual with floor shifter and Chrysler's three-speed TorqueFlite automatic was optional. Early four-speed '68 Road Runners featured Inland shifters, which were replaced by the more precise Hurst shifters during the course of the model year. Plymouth expected to sell about 20,000 units in 1968; actual sales numbered around 45,000. This placed the Road Runner third in sales among muscle cars with only the Pontiac GTO and Chevy's SS-396 Chevelle outselling it. Dodge debuted the Road Runner's cousin, the Super Bee, as a mid-1968 offering after seeing Plymouth's success with the Road Runner, along with demands from Dodge dealers for their own low-priced muscle car as the Dodge Boys started the model year with the higher-priced Charger R/T and Coronet R/T - both of which were priced similar or higher than the Plymouth GTX. 1969
The 1969 model kept the same basic look but with some slight changes such as tail lights and grille, side marker lights, optional bucket seats, and new Road Runner decals. The Road Runner added a convertible option for 1969 with 2128 droptop models produced that year. All were 383 engine cars, except for ten 426ci Hemi convertible cars. Six of those Hemi convertibles were automatics and four were four-speed manual transmissions. Six are known to exist. No 440 6-bbl convertibles were made in 1969. An Air Grabber option (N96 code) was introduced this year; it consisted of a fiberglass air duct assembly bolted to the underside of the hood that connected to twin rectangular upward-facing vents in the hood with orange vent screens. The fiberglass hood box had an "Air Grabber" sticker on the front. When the hood was closed, a rubber seal fit over the large-oval unsilenced air cleaner. A decal with Wile E. Coyote saying "Coyote Duster" was on the air cleaner lid.
The assembly ducted air directly into the engine. The vents in the hood could be opened and closed via a lever under the dashboard labeled "Carb Air." [2] In 1969 the 383ci engine was the standard powerplant, and the 426 cubic inch Hemi was the only engine option available for the Road Runner until mid year production. The (A12) 440 cubic inch engine option with three Holley 2 barrel carburetors was added to the lineup at mid-year. Several of the cars were ran in Super Stock Eliminator drag race competitions. As denoted on its fiberglass hood, Dodge marketed its three two-barrel setup as the "440 Six Pack" for the 1969 Super Bee. 440 6-bbl Road Runners had no wheel covers or hubcaps, sporting only "H" stamped steel wheels with chrome lug nuts. It featured an organosol black fiberglass lift-off hood with 4 hood pins and a large functional hood scoop with a red sticker on each side saying "440 6BBL". The scoop sealed to the large air breather.
All cars had a Dana 60 rear axle with a 4.10 gear ratio. Production of the 440 6-bbl A12 option Road Runner was approximately 1432. The A12 option had an "M" as the fifth character in the VIN. The 440 engine was rated at 390 hp (291 kW) @ 4700 rpm, and 490 pound-feet of torque @ 3200 rpm, the same torque as the Hemi but at a lower engine speed. This meant the stock 440 6bbl was about as fast as the stock 426 Hemi in the 1/4 mile, with its lighter motor and hood. This option, along with the standard 383 and the Hemi made Plymouth and Dodge fierce competitors at the dragstrip. The Plymouth Road Runner was named Motor Trend "Car of the Year" for 1969. Sales topped 84,000 that year.
1970 brought new front and rear end looks to the basic 1968 body, and it would prove to be another success. Updates included a new grille, leather seats, hood, front fenders, quarter panels, single-piston Kelsey-Hayes disc brakes (improved from the rather small-rotor Bendix 4 piston calipers of '68 - '69 ), and even non-functional scoops in the rear quarters.
The design and functionality of the Air Grabber option was changed this year to increase both efficiency and the "intimidation factor". A switch below the dash actuated a vacuum servo to slowly raise the forward-facing scoop, exposing shark-like teeth on either side. "High Impact" colors, with names like In-Violet, Moulin Rouge, and Vitamin C, were options available for that year. The 1970 Road Runner and GTX continued to be attractive and popular cars. The engine lineup was left unchanged although a heavy-duty three-speed manual became the standard transmission, relegating the four-speed to the option list along with the TorqueFlite automatic. This was to be the second and last year of the Road Runner convertible, with only 834 made.
These cars are considered more valuable than the 1969 version due to a better dash, high impact colors and more options including the new high-back bucket seats shared with other Chrysler products which featured built-in headrests. The relatively popular 440 Six Barrel was relegated to option status for 1970. The 1969 "M" Code Edelbrock aluminum intake was replaced by a factory-produced cast iron piece; however, due to a porous casting, there was a recall early in the iron intake-equipped 440+6 run, and these were supposed to be replaced with the more-desirable Edelbrock intake from the year prior. Sales of the '70 Road Runner dropped by more than 50 percent over the previous year to around 41,000 units (about 1,000 ahead of Pontiac's GTO but still about 13,000 units behind Chevy's Chevelle SS-396/454). This would also be the last year of the road runner convertible with 834 total production. Only 3 Hemi (R) code road runner convertibles were built. The declining sales of Road Runner and other muscle cars were the result of a move by insurance companies to add surcharges for muscle car policies - making insurance premiums for high-performance vehicles a very expensive proposition. Also, Plymouth introduced another bargain-basement muscle car for 1970, the compact Duster 340 which was powered by a 275 hp (205 kW) 340 Magnum V8 which in the lighter-weight compact A-body could perform as well if not better than a 383 Road Runner. Furthermore, the Duster 340 was priced even lower than the Road Runner and its smaller engine qualified it for much lower insurance rates.