Another alternative, and a heck of a lot cheaper one, is to find an upholstery shop and either have them install the covers for you and build out your original foam or just buy a piece of foam from them and do it yourself. That is the route I took. I think I spent about 10 bucks for a slab of high density foam from my upholstery guy and then cut, fit, and glued it to my seat tops. Now, hindsight is 20/20, if I had to do it again I would have built the seat up from the bottom and saved myself a lot of cutting and notching of the foam. BTW, my stock 76 seats with new MSA seat covers and the foam I added are the most comfortable series one Z seats I have ever sat in. Well worth the 10 bucks.................
Charles