If you have the 3 phase now, or can get it, you are most likely better off with that as the power source. I have a blast cabinet and my IR 5hp 175 lb compressor runs nearly non-stop to power that.
As for blasting a frame, I'd bet you would only do it once, as I did, with a 100 lb pot blaster. I had the frame on a huge tarp and kept sweeping up the sand, screening it and re-using it until it was dust. I started with 300 lbs and after 12 HOURS of non-stop work, I had run thru the equivalent of 900 lbs of sand. Never again. It's cheaper to just take the frame to a baster and then paint or have powder coated, as I have done twice now, for around $100.
175 lbs in your air shocks...
Isn't that like putting steel struts in their place for ride quality ?? Sounds really high.