R134a Conversion for 1992?

[KJL]

I have a leak somewhere in my system. I have not identified the source as of yet. I received a low refrigerant code 9 and verified with gauges. Yesterday I charged it with EnviroSafe refrigerant up to about 40psi low side and 200 psi high side at 85F ambient. It took about 6 ounces. It had dye in it but I did not inspect with a UV light yet. After a few minutes of driving the clutch disengaged and the code came back. For it to bleed down that quickly one would think it must be a substantial enough leak to easily identify. Before adding the EnviroSafe, the system had about 100 psi on the high side when forced to run. I have had this low pressure code for about a year so I am confused as to why it bleed down so quickly. I was expecting to find a small leak somewhere at some point. Anyway, is there a conversion kit to 134a for the pre-1994 cars? Could I swap in a compressor, accumulator, condenser and orifice tube for a 1995 ZR1 if they exist?