318 piston ring gap

I've been running around .014-.016" for decades with all sorts of engine in this range with stock ring heights and 3.6-4" bores with no blowby or other issues. The 340's KB hypers got a lot larger top ring gap, as did some Arias forged pistons in my new Opel engine, both of which have the top rings way up on the pistons.

BTW, OP, check ring side clearance before you try to re-use the original pistons. That has a BIG effect on the ring seal and blowby. Re-using pistons with worn ring grooves are a waste of time, and replacement stockers are cheap.