I have a complete fan and rad assembly from an mc5 - all yours if you can retrofit it, I will ship if for free.
Unfortunately, the MC-5 cooling fans and radiators are incompatible with the GMC 4106 design.
The MCI is a "T-drive", with the cooling blowers driven by a long belt from the crankshaft pulley to a compartment directly above the engine, with two radiators on each side of the coach.
The GMC, being a "V-drive", has the engine sitting sideways across the rear, with a single large radiator on the street side, with the fan being directly driven through the torus unit, no belts involved.
Generous offer, but sadly incompatible.
FWIW & HTH. . .