Well Fifth,
The first mistake is looking at the tank size. The tank is the cheapest part and is of little value in your case.
As soon as you look at any air compressor, look at the specifications. The first part to look at is "CFM at 100Psi". This is the money shot right there. In simple terms, 1Hp should get 5CFM at 100 PSI. If you plan to run it off 12VDC, 1Hp is about 60Amps so you better be real ready for that.
Matt