You have had some pretty serious contact, based on the pix. I would be checking the rod bearings.
As above, you absolutely need to measure the amount of height that the pistons come up above the deck with a dial indicator on the magnetic base. Set the mag base stably on the deck so that it does not rock, and check the top and bottom of each piston for its height relative to the deck. Rock the pistons back and forth at each measurement, note the highest and lowest heights, and take the mid-height as the measured height.
Then set the gasket thickness so you have .035" minimum piston-to head clearance, and a bit more, like .040" won't hurt. You will have a tight quench gap either way.
BTW, per nominal parts stack up, your Speed Pro pistons are nominally. .018" out of the hole. With a .039 Felpro 1008 compressed gasket thickness, you may have had just .020" clearance..... with that, it's pretty much a given that you will have piston-to-head contact at some point, with expansion and piston rock, etc.
Once you know that, you can calculate up the thickness you need. Cometic has them pretty much in .005" thickness increments in the range you likely need. You can order direct form Cometic and it takes just a few days for them to make the gaskets.
BTW, make sure you do indeed measure the piston deck heights; DON'T guess. It may reveal a lot of things. We found uneven deck slope top to bottom (deck not square to bores) so had the block decking corrected. We also found one crank journal ground about .003-.004" higher than the others, so had those 2 pistons milled a bit more. And you might find uneven rod lengths. With you running pistons with the heads above deck, getting this right on every piston is very important.
