Measure the quench pads first. I've measured literally hundreds of them on both big and small blocks and unless someone has jacked them up with a grinder or decked the heads crooked the pads will be fairly close. Like within .020 at the most.

Clean them up and mill the heads flat. As long as you are within .020 on all 8 you are good to go.

Then just deck the block and stick the piston out of the deck. You don't need a custom piston to do that. I'm running my junk at .048 out right now. The heads I used were all within .010 so I cleaned them up, milled the heads to the chamber size I wanted and stuck the piston out of the bore to get the CR I wanted. It's not a sin or a crime to stick the piston out of the deck. Also, I've tried quench from .035 to .060 and even .090 and I couldn't get any quench distance to be more sensitive or less sensitive to detonation.

Obviously, you want the quench closer than farther away, but I've seen junk with a big dome and .100 quench make pretty remarkable power and not have detonation issues.