I would install dual pusher fans in front of the condenser, and yes changeout the pressure switch for one compatible for R134a pressures.

I also replaced my viscous fan with a SPAL 16-inch and in stop-n-go 97-F desert heat (Las Vegas) the A/C was still cool.

All this in a black 1988 W124 wagon that was initially filled with R12.

:-) neil