You'd want tighter than 45-50. I think w the long rods/2.2 turbo pistons you could mill the head/block enough to get .035-.040" but you'd have to do some valve relief milling on the pistons as said to get the CR pump gas friendly. Polkat I think your plan is solid, to get an efficient /6 (which means quench) for an economy build. Holler what you end up w