Yes indeed, the one found on your car has a few threaded holes that are metric and there also are some later ones that use a different seal than the o-ring that yours had from the factory for the manifold connections.
I have "been there, done that" with rebuilt R4 compressors with terrible outcomes. I would suggest buying a NEW one especially for your car. Also after flushing I would highly recommend a suction side filter. This is an aftermarket inline filter that you can put into the low side line near the compressor inlet. It will prevent debris that was left behind after the failure of the previous compressor from spoiling your new one. Some people even go so far as to say that with a suction side filter it is not necessary to flush the system. I find this difficult to stay away from, the compressor is not the only part that can be damaged by circulating debris.
If you just flat can't afford a new R4, go to www.aircondition.com and post there for a recommendation of a reliable rebuilt supplier.