I just set my restored cab on the restored frame. Installed new front mounting bolts, shims, and cushion. I read the factory assembly manual regarding the two rear shackles (this is a '51 3600), and it says to shim to .76, +.06, -.0. I'm guessing this means the rear of the cab should be held approximately 3/4 of an inch above the frame rails by the shackles, but can someone confirm that? Also, is there any kind of cushioning pad between the shackle and the cab, or is it the shackle that provides the cushion? Thank you very much in advance for any responses.