I run A/C on my 250 inline, it uses a Sanden 508 compressor from Vintage Air. The amount of drag on the engine is so small I can hardly tell it's running, rpm drops maybe 100 at idle. Every summer I just adjust the rpm up slightly. These new compressor are not like the old 6 cylinder GMs. If you run the belts right, a single groove pull would work if you could get enough belt to pulley contact on each accessory you want to spin.
