Not to put a damper on your happy but our 1990 Bounder had a cobbed together dash unit. My biggest problem was the cheapo plastic vacuum lines that disintegrated. I think you will find that hard as it may be in your area, that repair is cheaper than conversion as is total replacement.
Conversion is okay and pretty cheap initially but beware with extended non-op time the system will fail again. The 134A refrigerant will not work as well as the original R12 in a system designed for R12.
Look up a guy on here I believe his handle is GoldenHVAC. He is in CA but is really happy to help and is very truthful. Whatever you do, DO NOT let a mechanic screw with your AC.......
We just bought the Adventurer in my signature and after a week the AC was dropping out on hills. Had it happen before, cheapo vacuum line in front of firewall was bad. Bought some GATES vacuum hose and replaced the plastic. World of difference.