I know you said you weren't planning on tube bumpers for air tanks, but I just wanted to put this in. Remember how everyone was bashing using a typical tube-bumper for an air-tank because the welds weren't right for it? Well, you could just have the correct ends put on and welded the right way, along with the rest of the fittings, and it would work quite nicely. I've heard of some people putting air-tanks under the hood, and while it could be made to fit with an inline 4 or 6 I think it would be too hot in there and be constantly blowing the burst disc. How about on top of the rear fenderwells, between the sections of roll-bar? You could even strap it vertically to the roll-bar itself and not have to bolt it through the sheet-metal.