Air Bag Valve mount location?

[ccrane0044]

Hey guys, I'm starting to do the final build on my 80 C10, and just curious where people are mounting their valve. I have a, what they call an Air Engine, with all the valves attached in one location. I was originally goinf to mount it inside that cab but recently thought that somewhere on the frame rail or firewall would be better. Please offer your advice.

Thanks guys.

Also here's a few pictures of where I'm at so far...