500ci rebuild steps...

Hi

I just took the heads off of what was supposed to be a good running engine and this is what I found in all the cylinders. It's a 400ci block from 73.

I was given paperwork for this motor and I see that there were Speed-Pro rings the size of 4.375" with .005 oversize (part# R-9799.005). There is nothing about pistons used and I can't find anything based on part # visible on the piston but I'm guessing they are 4.375" given the rings used. I did not measure it yet, I will next time I have a chance to spend time with it.
It was supposed to be heads swap for TrickFlow 240s and where we are...

This motor did not smoke, did not need oil between yearly changes, made power and started right up. All spark plugs look like the one in photo. Oil was clean, just bit dark, filter had no suspicious elements in it. Also cylinder pressure between 130-140psi on all pistons, idled really nice and had really good oil pressure. So yeah, lets upgrade the heads having this nice healthy motor...

So enough bed time story and to the point:
I see that Icon makes forged 4.382" pistons and 4.402" pistons.
My question is what is the biggest acceptable bore for 4.382" piston?
I'm asking because looking at the bores I think there needs to be like .006-.008" taken off to clean them up so this puts me at 4.388-4.390" bore. I would really like not to do .060" over without trying .040" first...

Thanks for your input.