I think Miltech use GI parts, including receiver and barrel. $1K would be a good price, as they are fairly thorough. Since Fulton uses cast receivers, and Miltech restores GI forged, I would go with Mil-tech.

I am retired LEO (and Armorer) and carried a USGI M1icon Carbine as my primary trunk weapon for much, if not most of my career. I'd do the springs as I stated, use ONLY GI 15s and GI 30s for mags, and good ammo. Hornady Critical Defense carbine ammo is awesome, though I used Remington 110 JSPs. in mine. I took a 200 pound BlackTail at 97 yards with a single heart/lung shot with it in 1988 or so.