...with the downsized cars coming in for 1981, only the big money teams (Petty, Junior Johnson, etc) built all-new cars. Most of the low-buck/backmarker teams cut down the earlier cars: shortened the wheelbase behind the roll cage, and rebuilt the upper part of the cage to fit inside the downsized bodies' roofs. When you look at photos from those early Eighties races. the lesser known cars will have huge flares over the front and rear wheels...signs of a cut down Seventies chassis. The MPC downsized stock car body (all had a Buick Regal body, with different hoods and front fascias) had the flares. Of course, the chassis in those kits was the generic unit from their Seventies kits, just like some of the 1:1 cars...
--Mark