The best/cheapest way to make 4x4 would be to get the T-case and axles, drivelines, from a military 2.5 ton truck.

4X4 back in the day used Timken or Rockwell axles,with a divorced Timken t-case, but finding a decent parts. would be tough.
IMO.
Tom

1951 GMC 650 Diesel
1958 GMC 550 Wrecker
1964 Chev C-80 427cid Tandem
1947 Dodge WDX Power Wagon
1977 Chev K-30 400 cid
1984 Chev K-30 Cummins 6BTA