Using 0.039" compressed for the gasket, zero deck, 5 cc's in the piston eyebrows I get 11.08:1 static c.r. I don't see how you could get to 11.72 with flat-tops in a 350. Even at 11.08, the cam's too short.
Anyway, with that much compression, start with a gap of 0.035". Widen it a little at a time to experiment, depending on your ignition system and the coil you're using.