383 Build - Help!

i agree with this. those pistons should give you some pretty healthy compression being about .020" below deck, but measure it. looks like you'll have about 12.5-1 compression. i'd say use a good felpro headgasket and you'll still need to use premium gas. i'd look into a gam like the mopar 484 since you using those restrictive shoemaker hearders.

That KB piston won't give hem anything remotely approaching 12.5 compression in a 383 with a stock stroke . the KB400 has a dome and is rated at 10.0 , those look like flat tops , he'll be lucky to have 9.0 , depends on what the chambers on the heads are cut to.