I also would say just go ahead and convert it over to R-134a. All your hoses & seals are over 20 years old now and everything probably should be replaced anyway.
I converted my '90 to use R-134a back in '08.
Replaced the original compressor (leaky) with a new OEM-type one (Visteon FS-6), replaced all the hoses, accumulator & orifice tube (red), and flushed out the stock condenser & evaporator with solvent. Did the normal evac routine and then charged it up with 32oz R-134a freon and 10oz PAG oil and it now blows out at a nice chilly 38° on full blast.
Total cost was around $700 or so in parts (the compressor being the bulk of it). A cheap reman compressor would've saved a bundle, but I didn't want to take a chance with having it only last one season or something so I went ahead with the good stuff as much as I could.
Oh and to get those little cans to empty out all the way, place it in a pan of hot water. :icon_thumby: