317 are 72cc cambers, great for adding more boost. You lose a little power off boost as the only cons that I see. In higher HP 900whp and up, the 317's will not push water as easy as other factory heads as they have the thickest deck of any GM castings (GM LSX casting excluded of course). 800whp and lower, with head studs and a good MLS gasket, I don't think it will matter.