I always thought they were the same too with 3 different ones (6, V8, Hemi) but there are multiples listed in Galen's book (page #47 in July 2006 casting guide - and at least one he doesn't have in his book but did decode on my 70 Cuda - 72 coin) and the interchange manual gives different ones too that differ in part number besides the skid plate.
Having said that, I know a guy with a b-body K-member in his e-body (but he is looking to change it) so about anything should work on a V8.