I know on my E34 BMWs, the later models that came from the factory with R134a had a slightly larger (though not parallel flow) condenser to make up for the reduced cooling capacity. That makes for an easy upgrade since it's already set up for the existing mounting points and hoses.

I wonder if a condenser from a 94-95 W124 (with an R134a factory fill) would be a similar upgrade for you? I would imagine it would be much less work than fabricating the hoses and mounts needed for an aftermarket PFC.