I have a bulgarian stamped metal side folder mounted in a russian AK100 series trunion. It latches closed ok, but it's a little loose. It locks open tight and solid, but between open and closed, it wobbles. Not really a show stopper, I guess, but it bugs me.
I suspect you could not do a swap the other way, i.e., AK100 series stock in a bulgarian stamped side folder trunion because the big ak100 pin won't fit... but maybe you could use the skinny pin, and have another floppy stock, I'm not sure. It would be less than ideal, imo.
~Doug