Pistons either stock or replacement will be the same weight within factlry tolerances. No need to worry about that. (I assume you are not buying one lightweight custom forging!)

You can put new rings on whatever piston you end up with, just lightly run a ball hone through the cylinder. Actually, I have replaced rings with NO disturbing of the surface and they seated right up.

Compression height problems? Forget it. I know guys who circle track raced engines with three different compression ratio pistons, from three previous engines. The car ran good, no indication that everything wasn't kosher.

Heck, you could pull that piston, take off the rings, put a new set on except put the top ring in the second groove, put oil ring where it belongs, and run it that way! There are two-ring pistons running on racetracks. Three is not a magic number. Just like four was not a magic number back in the day.

You're not doing a restoration, you're trying to get a car to move under its own power long enough to be sold. Be honest, tell the buyer the truth, "the engine will need to be rebuilt." You don't need too go into specifics why. If you're telling him it needs to be rebuilt that covers whatever is wrong inside.

Good luck with that HOA! I bought my house specifically because it didn't have one.

R.