I would use the old york compressor if I could modify bracket to change pulley or make a lighter bracket, that bracket is a monster.I also wonder about the control, can you adapt a newer controller to operate the compressor? The one in my car was toast.I never even had a belt on my system but I know it had an idler pulley, does the newer ones mounted lower left use an idler pulley?

The 74-78 factory systems use an idler pulley, the after market ones don't. My 78 has an ARA system with a bracket that allows adjustment of the belt.

it seems to me that the left side would get pretty crowded compared to a right side mount system. There is lots of room above the alternator especially if you eliminate the mech fuel pump.Plus the lines are a straight shot from the right side.

The early systems have the hose fittings on the right side of the condensor. The later aftermarket systems have the fittings on the left of the condersor, the receiver/drier on the left side, and the evaporator in the center of the car behind the heater control panel. The ones with factory air have everything on the right except for the compressor with hard lines that go accross the radiator support to the rec/drier and evaporator.

I need to get out more to study these cars, not to many z events in Indianapolis. Thanks for the info, didn't realize the evaporator was moved towards the center which makes more sense for the left mount

In my 810 which has factory air, the evaporator is on the right which makes it real easy to remove. I was able to buy new components for that car for less than 400 bucks thanks to OEM surplus (compressor and evaporsator), Standard Air Products (receiver/drier), Master Auto Parts (condensor), and Nismoparts.com (expansion valve).

I checked the unit with the pulley attached to it and it says "Diesel Kiki" and "Made in Japan" underneath that. It definitely wasn't installed on the car by the original owner but more recently. I guess there are a variety of aftermarket options and the PO just picked one.