Thanks Engatwork for the advice.
I have the R-12 (5, 12oz cans -- **original Cold Shot cans acknowledging Jackd's response below) and a manifold gauge already so I'm pretty much ready to break down the system.
I'm trying to determine how many O-rings I'll encounter and thus how many I'll need to replace. Looking on Fastlane is really no help. It looks like there are 4 that go on the exp valve alone, and 2 on the compressor suction and return lines and I'd imagine a couple more btw compressor and condensor.
Again, thanks for the help!