1970 and 1971 use the same bottom for Challenger and Cuda. The seat foam is different for the years and seat style. Although the foam is the same for Challenger 71 deluxe and 70 SE cloth. The tops or backs are year specific. 70 and 71 are different. 70 upholstery will fit the 71 seat and visa-versa. The difference is in the seat release latch button assembly that operates the tilting seat back. 1972 up is the same for Challenger and Cuda. They are the same tops, bottoms, and foam for Cuda , Challenger 1972, 1973, 1974. It is possible that the bottom is the same as 70-71. For some reason I remember different. Can someone post a pic of the 72 up bottom without the back bolted on? I don't have one here for comparison.
Tod