When doing a legal conversion or when buying spare parts for an M2 or M2 kit, look out for reproduction parts. Most of the parts at the shows are repro, and are too light and/or soft to stand up to FA fire. This applies especially to the thin repro disconnector levers but also to disconnectors, sears, and selectors. There is still a good supply of 15 round GI mags, but a lot of the 30 round are also repros and I have seen some that wouldn't go five rounds in FA without a jam.
In addition, you need a heavy M2 stock, 4 rivet handguard, round bolt, and new type recoil shield to make sure things stay together when shooting. It is also better not to convert a carbine that has a recoil spring tube, as sometimes the receiver will crack at the tube seat.
A word to the wise. In the U.S., ATF has been known to hang around gun shows and watch some guy buy conversion parts, then move in and make the arrest. The usual situation is that a dealer will avoid arrest by not having all the parts, so a buyer has to go to several dealers. When he has everything he needs, he finds something he very well doesn't need.
Jim