Mounted the Pickup Cab on the Frame - :(

[Brace Bailey]

Driver door is sagging badly - so I decided I had better mount my sandblasted and repaired cab on the frame to see it that would help.

No help on the door.

BUT>>> the front blocks are on top of the welt - no problem
Row of blocks under the seat front - about 3/8" gap between wood and body.
Rear, narrow blocks - behind seat - about 3/8 gap between wood and body.

Rear of cab (new lower panel welded in and the body pudy in the picture) - is sitting on the welt.

So, I've seen on some earlier posts that there may be "rubber" shims of 1/8" or 1/4" required for the mid and rear blocks. Do I shim with them to get the
rear of the cab off the frame?

and how how much clearance between frame (or frame/welt) should I have?

Hate to start cutting the welded panels out....