[25stevem]

Check the ring land clearance, if they are on the loose side ( more then .004” ) that can add to piston rock.
Loose top ring and oil rings will do this.

[lust4speed]

Custom order the pistons and just round up what is needed. If your bore is now a nominal .040" over there is a good chance that it can clean up with honing to .045". Best to leave as much wall as possible, and piston companies can do any size.

My old drag car engine was freshened every so many years and we'd have the machine shop just do a light hone and we would drop in another set of file-to-fit rings. Last freshen before getting new pistons we were at .012" piston clearance. Just getting our money's worth out of the Ross pistons. Surprising that we couldn't hear any piston slap even with a set of mufflers so we could show up for a local test and tune night. Had to be plenty of piston rock which rounds the rings and eventually leads to blow by and loss of power. In a street engine probably 10k to 20k miles, but never gave us trouble to the next complete rebuild where we didn't push things further and finally retired the old pistons.

[Dragncar]

You could do like the Boss Bird fellas do. Treat every cylinder like a single piston engine. You can buy just one piston big enough to clean up that one bore and Total Seal will sell one set of piston rings.
You engine will not know the difference. Might have to re balance.
Good Pontiac blocks are getting hard to find. Might as well save what you have.

[prostreet64]

Thanks guys. Definitely some options to consider. Will know more where we stand in a week or two.