Yes its usually trivial from a direct .gov perspective to register .mil equipment. One of my dad's friends had a used 5 ton truck (or was it a 2.5 ton?) for construction hauling, more for the impact and advertising than economics. This varies by state but virtually all states have an antique / kit / custom car registration category thats quite reasonable.

Unfortunately getting insurance on antique / kit / custom cars can be a little problematic if you intend to heavily use the vehicle. So you can get insurance for a 5 ton or an original ford model T or a modern kit car replica model T relatively cheaply and easily IF you stay under 500 miles per year on the odometer. It would be quite unaffordable to insure if you commuted 40 miles per day like my little commuter car.