Hi Jon,
Does that mean you are missing the idler wheel and bracket too?
If so unless you can cross match, the compressor on the left option might be easier to engineer from scratch. Looks like they are interchangeable as no other bit of the a/c changes with the compressor change.
8 bits idea on a new condenser is also a smart idea as the STD system wasn't good on the old R 12 gas and is less effective with r134' so a bigger condenser(rad) will help make it more efficient. On the 610 the system is bigger all round and is powerful enough when moving, but withi the drop in gasses the rad is not as efficient as it should be and they struggle when the car is stopped or moving slowly. If I ever move to r134 I will put in a more efficient condenser at the same time to get the effectiveness back.
Of course you need a/c on a 610 to maintain it's lard ball status with the more performance orientated members of the club.
Sounds like this could be quite a project...
Lee