The Plymouth Road Runner of 1968 :

Plymouth decided that muscle cars had gotten too far from their original purpose: cheap and very fast. They believed that the young buyers wanted all the hood scoops, decals and a big powerful engine on a low budgeted car.

So they would need to put in a car a full complement of performance-look accessories, but the product would have to have a low production cost, so that list price could be low.

The initial plan was to use the 440 cid engines as standard power unit. But the 440 would be more expensive than a smaller one; also they feared that it would cut too much in the GTX sales.

So they've used the next biggest engine, the 383 cid four-barrel with some modifications. "The engine had to be unique, something that could not also be found in dad's sedan." The 383 cid was treated to the heads; manifolds, camshafts, valve springs, and crankcase wind age tray from the race ready 440 Magnum.

The interior was very basic, bench seat and no carpeting, just rubber floor mats.

To duplicate the "beep beep" of the Road Runner, Chrysler spent over $50 000 reworking an old military horn to capture that peculiar sound. The short development period explain why the horn was in black 1968, and purple with a decal from 1969 to 1974.

You could also for an extra, get 426 Hemi.

The Road Runner was a big success, originally Plymouth estimated that they would sell around 2,500 vehicles in 1968; they actually sold 44,598 copies.