I have close to 3/4 inch gap at the front and close to 2 at the back.
If you're talking cab mounts, 2 inches is WAY too much at the back. With the cab sitting nose down, that much, you'll likely never get the hood fitted correctly.
The rear cab floor should set on 3/4" boards on the frame, then install the shackles, shimming between the top shackle mount and floor if needed. The front also may need to be shimmed, and the spec is 1-3/4" from bottom of floor to top of frame.
