+1...jealous here too. Your treadmill motor idea is brilliant. You could simply direct drive the A/C compressor and use the car's A/C clutch input to trigger a relay for the motor, if the power steering power was kept separate. I have wondered if newer electric power steering racks could be fit into older cars like yours and mine. THAT would make things easier.
I have also contemplated refrigerant compressors for portable A/C units, powered by an inverter. Probably a colossal waste of power. Or maybe:
Maybe not.