R12 and 134 do use different oils, and the two oils are not compatible
A new 134 compressor will function in an R12 system. You would need to confirm the factory filled oil in the compressor is compatible with R12, or do a flush if incompatible
The new 134 compressor will have O-ring fittings. These fittings can be adapted to the R12 hoses’ flare fittings with these adapters
Hope this helps
Larry