I'm pretty sure it is hydraulic brakes. It looks like a brake pedal all the way down to the floor. This is what air brakes would look likel

https://plus.google.com/u/0/1126369...6411612146&oid=112636930370126476644

Also, I don't see any air chambers in the picture from the rear. And I'm not sure they made brackets for a compressor for the Pontiac engine. The engine would probably be a 336 Pontiac. The transmission might be a New Process 540 or 541. The suspension appears to be Hendrickson and the rears appear to be Eaton. It could be one of those goofy Eatons with the drive shaft going to the rear over the forward axle instead of a throughshaft like Rockwell used.

A first glance, it looks like one of the food service trucks at an airport, but it is way too heavy for that. Just a wild guess would be that it was used to load weaponry into B52s.