[dsraven]

strip down to the steel springs, repair as required, cover in uphostery foam of your choice for density, contour the foam to your desired contour, cover that with a thinner less dense foam (spray glue from an upholstery supply place, I use a 3M brand but don't remember the number of it), then cover with your choice of covering. there are also things that can be sewn in to the covering to keep it shaped to the foam contour, like a stock seat in a modern vehicle which uses something like a velcro strip glued into the foam and the corresponding spot of the seat covering. I have also seen a lot of seats from 88-98 chevy trucks used. they have a straight bench from a regular cab or a 60/40 split bench with independent fore to aft adjustment and a fold down arm rest. the head rests come off so the seats will actually not stick up past the back window and will also allow the seats to go back further before they contact the back wall of the cab. if you wanna keep a stock seat base but have a more contoured feel you could find a seat that is the same width and steal the contoured foam from it?
just a thought or two.