Fitting adapter kits can take an r12 unit to 134 fittings, but I don't know if a 134 can be taken to r12 fittings.
If you're replacing your old York compressor and still have the original hoses, they should be replaced with vapor barrier hoses. The A/C shop that makes your hoses can put either type fittings on the hoses depending on your requirements.
Dan
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