The old systems were designed to work with R12.......I can only speak from my experience...Years ago I switched my Factory Air 66 Chevelle over to Freeze 12 ....I drove the car for a month in the Summer before switching back to R12....It lowered the air temp inside but "Never" cooled the Inside.......The old systems are Designed and Balanced to work with the R12 and everything else (with the stock components) is a compromise..........
Ken
