[Pyrotechnic]

You can run these systems with R134A just fine, you just need to change out o-rings, get a new dryer, and the biggest thing is to flush all the oil and trash out of the system so it is CLEAN. It won't be quite as cold as R12 but it will work.

For optimal performance, an aftermarket parallel flow condenser is the way to go. R134A needs a condenser with a lot of cooling capacity to work well, and the stock tube and fin condenser just doesn't have the cooling capacity for R134A to work well.