I've been asked to convert 3 x 70kw Carrier air cooled DX condensing units from R22 in preparation for the phase out of R22.

The units are single stage 6 cylinder semi - hermetic compressors (76A flc) with no unloaders. They appear to be recon compressors and operating quite satisfactorily.

Which gas should I choose?

It's an air conditioning application presently evaporating at 5C.