I charged an R12 system to R134 on a 72 Charger. Replaced the dryer on an original type and had a tech evacuate the system and charge it with R134 oil and freon. It worked great and ran for two summers and then the compressor locked up on the way home from the Nats. I understand the cause of the failure was either not all the old oil was evacuated or the higher system pressure of the 134 or both. The answer to your question is in my experience it will work but other problems will probably shorten the life of the compressor. FWIW I changed the entire system over to a Sanden compressor with a new dryer and hardware. Still running the old condenser.