I've had every car that was R-12 converted to 134a. For my Firebird, nothing was changed, the system was evacuated, the fittings were added and 134a was put in. I remember the car when it had R-12 in it, would leak out every year and my dad would have it charged the following spring. I converted it 3 or 4 years ago and is still blowing just as cold as the day it was done, so it wont leak out of the "old hoses." It's also just as cold as the R-12 was, if not colder, despite what all the people say about conversions. My GF's Town Car & my Town Car have been converted, all of those are going strong, nice and cold. I highly recommend it. If they have to replace the receiver/dryer thing it will bring the cost up some but should be less than 300. I think my Fireturd was done for 180 or less. Well worth it.