Thanks for the replies guys. I know in my head the system is safe in the back area (or else Corey&everyone else wouldn't be doing it) but I have some irrational discomfort with it. totally illogical on my part.
I have this image of the top bursting off, bouncing inside the truck and going thru my head! I know, there is a valve and it wouldn't even do any of that. I'm just nuts!

Anyway, thanks for the suggestions on mounting- it gave me some ideas. I'm glad to know about the bursting disc and that the PT's well within those pressures.

My friend has a welder so I'm going to try a bit of mounting fabrication after I buy the PT.

What do you guys think of this unit? saw it on ebay.
http://www.cramerdecker.com/offroadair/products2.html#1

 

Looks nice, but take notice it's setup like the Power Shot, no adjustable regulator on it.
Only good for airing up tires, no air tool useage.

You'd have to get a new reg for it.
This is why I did not mind spending the $300 on my PT, as it's a complete setup, nothing else needed, and all high quality parts.