Ya want what ya want.
The ar15 would need a new FSB and threaded muzzle. The FSB is taper pinned and a new FSB would have to be drilled and reamed to match the old pins...that resembles work (risk) and they might want a few more bucks for that. The simplest way to convert to an unbanned rifle would be with a new pre-ban type barrel.
There is a fairly expensive aftermarket tele-stock that I enjoy having on my pre-ban carbine, the MagPul M93, but I wouldn't hesitate to recommend an A1 style stock, with a trapdoor, to anyone.
The Belgian type FAL came equipped with a combo flash suppressor, bayonet mount that can be attached to a threaded barrel. Might be cheaper to have the barrel threaded in that case.
I don't know anything about the G3, except that it had a threaded flash suppressor. That can probably be reworked as well.