TorqStorm Supercharger build advice needed

The only thing I can think of is calling Wiseco. Since they offer the piston for the 198 rod conversion, they'll make a forged stock replacement, I'm sure. But as you elude to, they won't be cheap.
If you get the pistons made, consider calling Totalseal Piston rings regarding a recommendation by them on the rings before ordering the pistons. Do the research up front. Narrower modern rings create lower friction and wear. When ordering the pistons you will need to be able to tell them the rings you are going to use, the ring width and the required ring groove depth. Then you may be able to get the ring grooves hard anodized for durability and an anti wear skirt coating.
DSS may make pistons with their patented X grooves that spread oil from the oil ring across the piston skirt to reduce friction and wear. With the correct cam for a blower application I could see 275 to 300HP and reliable.