I did not have to weld any holes. The tromix trigger guard with the integral grip screw nut covers the old trigger holes with the pistol grip. The MSAutoarms internal stock adapter covers the hole in the rear of the receiver with the mounting bolts for the stock and also bolts through the receiver using the two holes originally used to mount the rear fire control - you would have to weld them shut if you chose to weld the rear receiver plate on. It was honestly cake to do.
One important note: the magazine counts as 3 parts - magazine, follower, and spring. As far as i can calculate, you cannot remain 922(r) compliant, using the russian magazine, without having a US made receiver or barrel, neither of which exist. I see people at the range doing this, but i dont bother them because i dont know them.