I would say the pad is 1/8" or so. You can shim more there if it makes the front sheetmetal fit any better. The bolts are just (2) carriage bolts that drop in from the top. If I remember right, there's usually a small rectangular steel plate on the bottom with a couple tabs you can bend over to lock the nuts in place. I don't remember springs being used here, only on the cab.

To be long remembered as he's cruising in
The Passing Lane