I have a ZPAP, and I'm not terribly knowledgeable about AK stuff. Do any old AKM bolt carriers work in Yugos, and if I keep the same BOLT in a new carrier, should the headspace be OK? Thanks.

I did not read it all. I'm an idiot lol

Yes you can swap bolt carriers as long as it's the same general type of rifle, piston length, etc.

An AKM carrier should work in a Yugo.

The only issue you may run into is that the bolt camming surface in the carrier may not agree with the camming ramp on the left side of the bullet guide. This is a common tolerance stacking point in AKs and can cause the carrier to bind if everything doesn't line up.

You shouldn't swap the bolt head itself without checking headspace.

Good info, thanks.