The compressor you have should be able to handle the pressures. I would replace the hoses with the barrier type. The 134 is actually larger in molecular size, this is why we use a 75 to 80% charge ratio to 12. Good luck with the conversion.
Be sure the temp switch is taken off of the drier and a trinary (late style aux fan switch is installed) . This will turn on the aux fan quickly and help with high pressure.
1992 500E (very soon I hope
1981 280GE SWB
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