I used a great "how to" article on replacing the seat back springs by screwing a 3/4" piece of plywood to the seatback and using poturpedic (sp) foam on the wood. Not only do you get a thinner seat with more room, it's 100% more comfortable.

1957 Chevy 10500 Fire Engine
1953 GMC 450 Pumper Tender
1957 Chevy 10500 Tandem Short Logger
1955 Second Series 3100
1957 3100 Shortbox
1957 Chevy 6500 Dump Truck
1957 Chevy 3800 1-Ton Flatbed
Lots of part trucks

Pix in Photobucket

"I haven't grown up, I just play with bigger trucks!"