Maybe I'm imagining things but it looks like the A/C compressor pulley must be "on" or engaged so it would pull the alternator which gets it power from the compressor. Can that be right?

It also looks like you could get a two groove water pump pulley and run the PS pump from it and mount it above and inside the alternator. It would require some fabrication but does appear to be at least one possible solution. It would then be one the left side of the engine or perhaps even swap it to the bottom A/C location.
Better yet check out the wrecking yards for 59-62 Impalas with PS and AC on a BlueFlame Six.

1953 Chevy 5-window 3100
In the Stovebolt Gallery
More pix on Picturetrail

Dave
Engine & Driveline Moderator

If you can't make seventy by an easy road, don't go. ~~ Mark Twain