I have a new set of floor pans for our el Camino. The contour of the pans at the rear isn't quite the same as what is in the car now. I think that they may be for a '68 and up coupe. One catalogue lists one floor pan number for '64 and up. Others show '68 and up as different. Are these pans the same as the 4 door pre '68? :-( HELP.