I too would suggest you read through all the discussions on this subject that have occurred in the past. Most of my opinions having worked on a few of these systems is to first make sure you have a good RV2 Chrysler compressor in the first place that doesn't have a lot of miles on it or an NOS one if you can still find one. Perhaps the most costly issue is trying to have one rebuilt since it seems no one makes a really good rebuild kit based on the number of failures I have heard about with the only rebuild kit I am aware of from a Florida source.
I prefer going with R12 since the few conversions I have heard about have not been successful with 134 for a number of reasons either because of not achieving suitable low temperatures unless you use a non-original temp sensing switch closer to the evaporator and premature compressor failures. There are only 2 suppliers of the really good Autotemp II newly remanufactured controllers and either one of them is fine. I also believe you would be doing yourself a favor and work with an A/C shop that is familiar with working on old cars that won't let you down. I am grateful to have a really good shop available near me in Ontario, California. AC Global makes good heater cores, evaporators, and condensers and have worked with Mr. Heater Box out of Canada that also rebuilds your control boxes under the lower right hand side of the dash assembly. That Canadian company is also first rate.
The only other option if you can't find an NOS RV2 compressor is maybe a rebuilt perhaps from someone who has really good feedback from a good number of sales he has made with 100% feedback - here is just one I found on Ebay today with 14 rebuilt RV2 compressors sold - and still 100% feedback:
RV2 A/C COMPRESSOR WITH CLUTCH FITS MANY CHRYSLER AND DODGE WITH DRIER AND VALVE | eBay
Best wishes and none of this is inexpensive...................