If I was buying one to rebuild as a semi, I'd have a blocking bar welded into it about an hour after it arrived in the mail......
About 90% of those "saw cut" kits you see for sale used to be torch cut , were rewelded, and then "old spec demilled" last week......
A fellow in TX ran afoul of the ATF for this exact same thing with "saw cut" Uzi receivers within the last year or two.....
The only single cut Uzi receivers I ever remember coming in the country were thru Armscorp in MD.......FN and IMI......and they were pretty much sold out by 1995