So then it should be fine as long as I fix that #6 cap and get it to at least .0020" with some heavy polishing/light turning? Any reason to go bigger than that?

Any idea as to what caused that super tight clearance on #6?

69 Buick Special Deluxe. Intercooled Turbo Chevy 250 @ 15psi on a stock long block. It's kinda fast.