, after 2001, it became illeagal to possess or install R12. R416 and R414 are acceptable repacements, however I have had two compressors fail (auto application) due to oil circulation issues. I'm not sure what the laws are in the USA, but here in Canada I use Duracool 12a. It is a hydrocarbon blend, and is a direct replacement.
is one discussion on the subject.