Seat foam for 66 Barracuda

How cabn the same seat foam be used for a & b bodies? I would think that it would have to be trimmed by the seat installer to fit properly. Especially if that is what they recommended. This may be the "base" to start with and need tweaking/trimming to fit whichever seat cushion you use it with.

The Plainfield Tamraz is only 10 minutes from my brother's house (60 from mine). They do not charge for shipping if you get any of their products shipped there and you pick them up, otherwise shipping can cost $$$.