Climate control functions and pressures should be very close to the same if the conversion was done properly with no traces of mineral oil left in the systems. The fill quantity of refrigerant for a w123 300D would be 2.64lbs (10% less than R12). Also the compressor should be "healthy" and a new dryer & switches installed. I run a factory R4 compressor that has worked flawlessly up to temperatures of 110deg for three years without any faults. I'm not sure if you have a W123 or a W124 300D so I uploaded both the factory pressure chart for w123 R4 & a generic pressure chart that would apply to the W124 Nippondenso compressor.
AC Pressure Chart.pdf
I hope this is what you were looking for!