Space is already limited in these trucks if you're at or above average height, most guys are cutting the seat mounts down for more room. We've been redoing a lot of 60's truck seats lately and have been repairing any bad sections of foam by cutting the area out, gluing new foam in place, shaping it with an electric knife, smoothing it with a 2" grinder with 36 grit disc, then using a 1/2" layer of Dacron instead of extra foam. It doesn't really add much/any height when you're sitting in it like foam would but helps the cover fit better and look smoother.
