An 80 up should have a R4 no matter whether 240 or 300.

No one that I know converts the York 2 cyl compressor. I haven't because they had so many belt problems that the extra head pressure sure won't help. Also none of them will take the pressure and oil if old.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician