Airtank mounting locations??

[randomhero472]

I would like to mount my airtank(s) out of sight, but have a blazer gas tank.. which leaves thinking about the only other place to mount them in on the frame rails in front or behind the rear wheels... i'm looking into doing (2) 3 gallon tanks, just because of their small size, although the 5 gallon tank doesnt seem much bigger, typically 1" taller and 3-4" longer.. my question is do any of you have pics of measurments of the clearance between a fleetside bedside and the outter frame rail, either infront or behind the rear wheels? i dont have a fleetside bed to use for measurements, and my truck will be leaving to be painted in a couple weeks, i'd like to get this stuff ordered by the time it comes back.. thanks