if you get one with an original generator, i would not use it until i took it off, had it professionally
cleaned, dipped, baked, fully inspected and made ready for service.
if a generator has been sitting around for years, it probably has moisture in the windings, or worse... mouse urine, either of which is hard on the insulation.
in my opinion going the extra mile to assure it is ready for service will probably pay off big time.
something akin to buying a 50 year old radio that has been sitting in someones barn for the last 25 years, you never want to power them up without a thorough inspection, maybe then with a variac to ease the voltage back up gradually, and generally replacement of all the capacitors,,, or else you run the risk of serious and expensive to repair damage.
same goes with old generators in my opinion.
bob g