Some performance shop, cnc machined aluminum to fill in the open deck block and pressed that stuff in. They turned a stock tt 350hp v6 into a 700hp+ monster and reliable too.The biggest v6 I've seen was 302ci ford svo engine. I don't know about the buicks but the svo's have been tuned to make 700hp n/a. Billet cylinder heads built with methanol in mind would be my goal.