what would it take to make a 5.3 into a forged 347? i know i can keep a stock crank but what piston choices are out there for a boost application and what -cc would i need to get a 9.5:1 compression with a 243 head and what head gasket?

 

You'll need a machine shop willing to do the work, and pistons, that's it. Slightly dished pistons in the neighborhood of -8 to -10cc will do nicely with a stock head gasket thickness and no more than .010" milled off the 243's.