OK, no quench gap; tnx TMM. I'm gonna say: Mill the heads and use the Felpro 1008 at .039" thick and then back up to the thicker 8553PT if the CR need to drop a couple of tenths. And milling the heads a bit for flatness is an excellent idea with older heads; if reliability is the goal, that is important. Glad the OP is looking at that matter. (I'd put money into that long before the money into any balance work as this engine stands.)
