I guess that's what I was looking for. The condensor is the real driver here to either convert over or stick with R12. Everything on my car is original.I think the answer to that all depends on the state of the current system and what oil is in it.
Regardless, you kinda need a blank slate and flush out whatever unknown oil is in the system. Any residual oil in the system will settle out in the condenser if it’s not compatible with your refrigerant of choice and decrease system capacity.
Full flush, and then inject oil in the qty listed earlier in this thread into the components listed.
If you are starting from scratch, there really isn’t an advantage of one refrigerant over another. The old condensers are a serpentine style condenser that is no longer available. Any replacement condensers are a new parallel flow type that works better for r134a. So if you have replaced the condenser for a modern unit, you can really go either way.
From what I understand, that part number seems to be the original one. If you have one, I would be interested.E4FZ-19A703-A