Barrels and sometimes barreled receivers show up on GB quite often. Numrich and other distributors sold a bunch of them. Forearms...well, you got a knife???
Welding/brazing that forearm lug onto the frame will be...interesting...
And you'd better set aside some time to tune it to your favorite load...
Check with Tom Heller...Seems like he mentioned something to somebody some time ago about a 16" barrel...