General knowledge.
4wd conversation are rather common in the light duty spectrum. Medium duty is another story. Very few medium duty trucks are 4wd from the factory, making parts hard to find and insanely expensive.
A front axle rated for 8000 lbs cost $8000-14,000 new. As stated gear ratios will need to match.
I have a pipe dream 1964-66 C60 4wd. Parts list includes a divorced transfer case (so I can use any 2wd transmission) np205 or np202 (found in 4wd 2 ton IH) and derating capacityand going with a Dana 60 front (rated at 6000 lbs).
The next issue is bolt pattern. And if you can live with two different patterns or if you get wheel adapter, most likely custom.
It will be just a little easier with the truck already having a straight front axle.
A few things like differential and drive shaft clearance, steering linkage need to be taken into account.
There are very few who have done it. And those that have usually say they wouldn't do it again. But you only live once right?
