Ah I've been down this trail. One word, Detonation. To much timing for the fuel being used. No piston, ring gap,or jetting is going to prevent that. My supercharged Volare small block ate pistons and head gaskets on a regular basis. Once I figured it out? Same pistons in it since 1991.
It looks like one of those cases of "I wonder what would happen if..." Well, you found out why there is special stuff for that kind of mod. Cool experiment, but now you have to build a new motor. Bet it was fun for a few minutes. Now you have the opportunity to build a supercharged 383, with all the right stuff, and it will be fun for a lot longer. It will only be as strong as its weakest part.
As far as compression. I had the same type of piston failure. More than once. Head gasket failure as well. Running 9 psi. It always had Av gas in it. Big ring gap. It ran cool. With only 7.9-1 compression. But it was running at 36 degrees as dynoed. Pulled the timing back to 29 degrees. Turned the boost up to 13psi. Never had another failure in 31 years. We ran my sons turbo small block at 22psi. Total timing was 21 degrees. Ran it for 7 years before we nipped a piston getting after the tune hard with a touch more timing. Neither car ever burned a strap off the plug.
36...yikes. Lol I know about wrenching on them.
On our 318 turbo car.... our last outing (as I recall in' 96) running av gas and 22 degrees we blew the head gasket. We were frustrated as it was our 2nd engine 3rd set of gaskets. Thinking we maybe had something warped we pulled the heads and had a laugh... on the gaskets all eight cylinders the fire ring was egg shaped and ready to blow into the valley, and one was completely blown. We were just running fel pro's and they were not up to the task. We had it as high as 18psi on a cold night....mostly we ran 9-12 psi but we really struggled with detonation....bad. We ran 3 different turbos, a switzer turbo on a draw through set up and two air research turbos on a blow through using a home made hat. Had a holley red pump with a 19 psi spring with a tweeked boost referenced regulator. We never made it to the track w the turbo. It either screamed or we had detonation....mostly had detonation. We couldn't afford any head gasket upgrades at the time. Pulled it and in went a slower 440.