I'm not sure, but I helped my brother converted his R12 A/C to R134a in a Suburan, he uses to take his family camping, last summer. He chose to do it while I was out there for a visit.
It was a much larger project than I or he thought it would be.
He needed to replace the compressor/clutch, the Receiver/Dryer (I suspect we may not have needed to replace it), an expansion valve, Conversion Kit (oil & new system valve stems), EPR Valve, and hoses because the fittings for the compressor were different sizes on the new one.
He had to run some stuff to clean out the system if I remember correctly. The R-12 residue would gunk things up he was told.
It was a bigger job than just changing some fittings, o-rings and coolant.
I believe he purchased some Freeze 12 on-line but then went with the 134a conversion.
But neither of us are mechanics. I do some DIY. This was more his project he figured he would rope me into, figuring if he had his big brother with a laptop to the Internet he could do anything :smile:
Good luck & keep us posted... I'm sure there are people who have been there, done this with their NSX here on prime.