well, the fleetwood is the only D-body... the rest share the exact same B-body carpet length. so any "impala ss" carpet will fit the rest(donno bout wagons tho).
I do think if you add 6" to a B-body carpet it will fit a D-body. Theres like 3" tucked up under the rear seat. I was gonna go the other way, and use the Fleetwood carpet in my Buick. I planed on either folding the carpet back 3" under the front seats, or stretching the back into the rear seat more.