Not sure how much this will help, but I recently completed the body off resto on my 76 and my body mounts were darn near rotted away (although frame was in good shape). There was little evidence of the shims left. I had to repair all of the flanges by welding on big washers and some judicious grinding so the shim fit up would have been a problem anyway (even if I had known how many I needed).
I took a lot of careful measurements on height to take my best educated guess at the number of shims I needed and hoped it would be close. That may have not been all that helpful as when I finally lowered the body back on - got the front and back bolted onto the frame - and installed all 8 mounts (torqued to spec), I was about 1/4 inch lower to the floor on the drivers side vs. the passenger.
All the doors seemed to shut nicely and I sure did not want to lift the body back off, so I just loosened all the mounts and front and rear frame bolts and then jacked up the drivers side of the body carefully (with bottle jacks spread out near the #2 and #3 mount positions). I fit one or two more shims into all the mounts on that side which seemed like the maximum I could fit, then lowered it back down and re-torqued all the mounts and front and rear bolts. When I remeasured heights on each side, it was still slightly low on the drivers side, but much better so I called it good. The front spring might be sagged a bit lower anyway since usually the car only has a driver in it. I should have measured the frame to floor height to get a feel for that issue, but don't think I did at that time.
If you want to know exactly how many shims I used at each mount, I have that information somewhere (probably would be meaningless for you though).
BTW - I went with poly mounts as I never wanted to do this again. They give the car a really solid feel (more so than with rubber), but the car was never very soft in the butt area anyway.
Hope that is somewhat helpful.
