Most likely, if the compressor's been off for any amount of time, the remainder of the system's going to need to be replaced as well. R12 + oxygen = corroded evap core, condenser and hard lines and deteriorated rubber hoses.
Hate to rain on your parade, but it's virtually a lock that if you put a compressor on it and charge the system, something else is going to fail momentarily thereafter. Unless you want to spend a bunch of coin on parts, your best bet is good old 470 AC.