Sugestions on a project

I have a 1984 GMC 6000 40' automatic transmission school bus i have converted into a motorhome which I use to travel and tow my jeep. I have been wanting to make it 4x4 for some time. It has a big block gas 366 in it on a GMC chasis with the old split rimmed tires on it. obviously i would have to replace the front axle and transmission and add a transfer case. Any idea where i could look to find them. and any sugestions/advise to help me do this.

Rockwell axles. But your project does not sound like a sound one. you might want to think about sell it and starting with a Fuso 4x4, a unimog or even a Pinzgauer. Even if you find the parts from a C5500 or 6000 they will probably be a buttload.