My 360 build.
Congrats on forging forwards on doing it yourself a leg. It is very satisfying to build your own mills. I love doing as much as possible myself.
As far as pistons go, I have used the Federal Mougal H116CP Hyper slugs and the Hyper KB-107’s that get you close. The Fed-Mougal’s below. The KB’s are ever so slightly taller. I forget how much but it’s nothing if your milling the deck. .001 *I Think!*
You can (possibly) find good deals on the Fed-Mougals if you look carefully.
If these are to tall, Ol’Kimmer has the shorter height slugs that can possibly spec out right for you. Measure twice deck the block once!!!