Shims Under Main and Rod bearings

OK on the pistons. thanks. You CR will be higher than I computed since I assumed the pistons were the truck style lower compression ones with the round recess in the piston top, as shown in the eBay picture.

Well, we can all understand debt. Is there any copper or any dark color showing through the grey bearing material in the old bearings?

AT-20 would not be a standard marking for .002" undersized, at least that I know of. Make sure that you measure each crank journal at least 2 places at 90 degrees apart around the journal. On the serial number pad on the block, is there a Maltese Cross symbol stamped by the block serial number? And on the number 3 counterweight of the crankshaft, is there an R stamped followed by some numbers?