I went with a CavArms A2 lower and a vietnam surplus no-bump A1 upper with FA. Looks like it was rubbed down with a cheese grater, but works fine.
I traded an old rifle for a bunch of Colt-made upper internals and a 20" chrome-lined surplus barrel.
I put a modern bird cage flash hider on it initially b/c that's what I had at the time, but I liked it, so I'm leaving it on.
The barrel is 1/12" so I'm locked into 55 gr ammo.
I don't know if they still have them, but Numrich had some grey 20 rnd aluminum magazines that made the look complete.
Great rifle. Easy to shoot.
I'm right about the metric system 3/4 of the time.