You're absolutly right the frame rails are identical to 70-74 Cuda' and Challenger, I know I parted out a 72 Coronet 4 dr in Florida and i already have the frame rails welded in on mine, beautiful fit and absolutly 100% identical. This is the drivers side frame rail from a 72 Coronet 4 dr on my 71 Challenger. Figured I would pitch a little help your way with the sale. Dave