Identifying the seals on the back of the compressor will also be important.

If they're actual O-rings, look for funola's compressor rebuild thread to get the proper oblong cross section part.

If they're rubber+metal sealing washers, you'll need to check if they're the black ones (2 same size) or the yellow and green ones (I think, maybe yellow and red). Regardless, if they're leaking they should probably be replaced.

You should also check to see if you have the high pressure cutoff in the receiver dryer switch. They should be installed in any 134a conversion. They're called something like bi-switch or dual-switch. They're still plug and play with the receiver dryer, but they're a safety valve on the 134a conversions. Not pricey, just add one to the R/D order.