[airdale94]

I would just replace the clutch. If you convert to 134 your A/C probably at the very least, won't blow as cold. And could, not blow nearly as cold. The problem is the condensor is smaller (front of radiator). Some vehicles have a upgraded 134 aftermarket condensor or you could try addapting one from a newer vehicle. Don't get me wrong it works, just don't expect that icy cold R12 air coming out of those vents.

If you just swap the clutch you don't need to evacuate the system. You need a clutch hub puller.