If it's the original setup, I'd say don't even bother with it. R12 is very, very difficult to come by, and costs a few hundred dollars per pound. I'm not sure the precise numbers, but these cars use quite a few pounds of freon. You'd probably be looking at a few thousand to get it up and running again.
You can also pay a few thousand to get a modern, R134 converted setup that'll bolt right in and work great. It might be the same start-up cost, but maintaining R134 is pretty cheap - usually about $35 a pound.
Jeff