Plymouth ‘Cuda 1970 AAR Alpine White

Only one automaker ever sold a factory street car wearing two different tire sizes front to rear, and it was not a styling decision. Plymouth needed 2,724 examples built in a five-week sprint to satisfy a racing rulebook, and Dan Gurney’s fingerprints are all over the result. This Alpine White AAR ‘Cuda carries a 340 topped with three two-barrel carburetors and a fiberglass hood. Read on for the rulebook that shaped every strange choice on it.

Look closely at the wheels on this car and something will seem slightly wrong before you can name it. The rear tires are visibly larger than the fronts, which is unremarkable on a modern performance car and was close to unheard of on an American production car of this era. It was not a styling flourish and it was not something a dealer did after delivery. It came that way from the factory, deliberately, for a reason connected to a road racing series most owners of this car never watched. That single detail is the thread that unravels the whole story, because almost every unusual choice on this ‘Cuda traces back to the same source: a rulebook Plymouth had to satisfy before it could go racing at all.

Built to Beat a Rulebook, Not Just a Racetrack

Plymouth entered SCCA Trans-Am competition by contracting with Dan Gurney’s All American Racers to build and campaign cars for Gurney himself and for Swede Savage. The series required manufacturers to homologate their entries, meaning a street version had to be built and sold in sufficient numbers before the race car was legal. Plymouth met that requirement by building 2,724 AAR ‘Cudas during a single compressed five-week period between March and April at the Hamtramck, Michigan assembly plant. The car was engineered with road courses in mind rather than straight-line bragging rights, which accounts for a specification sheet that looks distinctly odd next to its contemporaries.

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The 305-Cubic-Inch Limit and the Destroked 340

The engine rules were where things got genuinely strange. Trans-Am capped displacement at 305 cubic inches, which meant the actual race engines were destroked versions of the 340 small block, reduced to just under the limit. The street cars, however, had to carry the 340 in its full displacement, because what required homologation was the block and cylinder head casting rather than the specific bore and stroke used in competition. The result is that no AAR ‘Cuda ever sold to the public had the engine that raced, and yet every one of them was essential to that engine being allowed on the grid.

Three Two-Barrels and 290 Horsepower

What the street cars did get was a 340 topped by three two-barrel Holley carburetors on a special intake, rated at 290 horsepower, which was 15 more than the standard four-barrel 340 produced. The six-barrel setup ran on the centre carburetor under light throttle and brought the outer two in progressively as demand increased, giving the engine reasonable manners in traffic and a distinctly dramatic character when opened up. It came standard with a close-ratio four-speed manual and an 8¾-inch Sure Grip rear end carrying 3.55 gears, with 3.91s available for buyers who wanted the acceleration and could live with the highway rpm.

The Mismatched Tires Nobody Ordered on Purpose

Which brings the story back to those tires. Goodyear supplied them, sized G60x15 at the rear and E60x15 at the front, making the AAR ‘Cuda the first modern American production car to leave the factory with different tire sizes front to rear. The logic was straightforward for a car built around road courses: more rubber where the power is delivered, less unsprung weight and less resistance where the steering happens. It reads as completely ordinary practice today because every serious performance car adopted the idea eventually, but in 1970 it was strange enough that dealers fielded questions from buyers convinced something had been fitted incorrectly.

A Suspension Built for Corners, Not Stoplights

The rest of the chassis work went well beyond fitting stiffer springs. Special sway bars, heavy-duty shock absorbers and raised rear leaf springs were fitted, the last of these partly to create clearance for the side-exit exhaust that ran out ahead of the rear wheels. The lightweight fiberglass hood with its functional scoop, hood pins, strobe side stripes and the red, white and blue AAR shield finished a car that looked exactly as purposeful as it actually was. Very little of it was decoration, which is unusual for a period when stripes and scoops were frequently doing no work at all.

The Twin That Dodge Built at the Same Time

Dodge built its own version of the same idea simultaneously. The Challenger T/A used the same six-barrel 340, the same basic homologation logic and much of the same hardware, wrapped in the longer-wheelbase Challenger body, and roughly 2,400 were built. The two cars are frequently discussed together and just as frequently confused, though they differ in proportions, trim and detail execution. Between them they represent Chrysler’s entire homologation effort for that season, and the fact that both were built in single short production bursts explains why neither has ever been common.

How the Racing Season Actually Went

The racing itself did not go the way anyone at Plymouth hoped. The season was difficult for the All American Racers effort, and the manufacturer’s championship went elsewhere, with Ford’s Bud Moore operation taking the title. Chrysler withdrew from the series afterward, which means the entire AAR ‘Cuda programme, from homologation through to abandonment, occupied a single model year. That short life is precisely why these cars are so distinctive. They were built to serve a purpose that evaporated almost immediately, leaving behind a street car whose every unusual feature commemorates a campaign that lasted one season.

Alpine White, and What Survivors Bring Today

This example wears Alpine White, one of the more restrained choices in a year when Plymouth was selling colours named Vitamin C and Lemon Twist, and the contrast between the quiet paint and the strobe stripes works unusually well. Values for documented AAR ‘Cudas have climbed steadily as collectors have recognised how brief the production run was and how much genuine engineering separates them from an ordinary ‘Cuda. Matching-numbers cars with their original six-barrel intake and correct fiberglass hood sit at the top of that market, and the fiberglass hoods in particular have become difficult to find undamaged after fifty years of use. Original six-barrel intakes and the correct side-exit exhaust components are similarly scarce, since both were routinely replaced with conventional parts by owners who found them impractical. A car retaining all of it, in its original colour, is a considerably rarer thing than the 2,724 production figure alone would suggest.

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