80’s 318 compression ratio figuring out where I’m at.

I'll suggest taking the scale to the local machine shop with a piston and making sure your scale is close. (Or use some other calibrated weight in that range to check the scale accuracy).

Then just carefully weight the pistons, pins, ring packs, and rod bearing pairs (and locks of being used) with your scale to get average weights for each item. Then you can take those weights and use these small and big end weights, which are what I have weighed for a couple of sets of unmolested heavy rods:
(And if anyone has other such numbers, I'd like to hear them.)

These get pulled in to the standard formula for bobweight.

Make sure your shop is OK with this procedure; one fellow on here had his shop refuse to do it this way.

I'll PM my email and phone so you can contact me direct if you like.