Sounds like a sweet truck. If it's a 4 speed, it has the SM420 tranny. Divorced Rockwell T221 transfer case...check it for leaks. If you let it leak down it will grenade itself.
Front axle is a D44 with drum brakes. Not sure what the rearend would be, 12 bolt, D44, or the semifloater Eaton. Gears are probably 4.56.
You could get 6 lug axles with disc front brakes from a newer 1/2 ton 4x4 pickup, blazer, or burb, but you might have to move spring perches and shock mounts. 3.08 or 3.42 ratios would work well.
