I recovered my back seats with new covers. The local fabric store sold foam in whatever length you needed starting at 1/4, 1/2 and 1" thicknesses. I added 3/4" to the bench and 1/2" to the back. Spray glued the foam layers together and to the original seat foam. Warm sunny day and extra hands to hold the vinyl while I hog-ringed to the frame was a big help. As long as your base foam is good you can add a little more height as needed.