Shop air dilemma

I see some good advice above but the "King" of compressor specs for blasting has only been casually hinted at a few times-

CFM, CFM, CFM.

CFM is the king, almost nothing else.

Gallon capacity can be zero. PSI can be 75.

HP does factor, but again-

CFM, CFM. CF'n M!

I'd advise to get the highest CFM@90 240V unit you can afford.

...and I'd also advise at least 15-20 CFM@90.

Usually it will be a 5HP or more motor, and a 60-80 gal tank.

Don't shy away from a smaller tank. The CFM will more than make up for it.