File to Fit Piston Rings

I’m putting together the 496 (383 stroker) and I’ve got a couple questions.

The total seal c9190 65 rings are ‘file to fit’ and I’m wondering what clearance you guys think I should go for. It’s a street car, will be a very mild cam, -20 dish pistons.

Another question, do I only file the top ring or also the lower one?

thanks in advance
Author: Dylan Galvin