The original Argosy chassis was a Chev P30 and was not changed by Airstream much if at all. Belts, hoses, carb parts, fuel system, manifolds, water pump, AC system ignition system, cruse control and cooling system were all standard P 30 stuff.
Unfortunately, if some previous owner modified the systems, there is not a whole lot we can do on the forum to help you out. Anything could have been done and only guessing on our part would be what you would here from forum members.
If you want to restore it to original though, it is straight Chev P 30 chassis stuff from 1975.