Would there be guntrucks from different battalions or companys on convey's.

Yes this is correct.It was and is not uncommon to see gun trucks from different units being tasked together. I have seen where a truck would come off a convoy and be assigned to another going back immediately. They would change out the driver and some of the crew if they needed to and service the truck and head out. I have seen whee they had combined two or more convoys and reassigned the trucks to be in formation about every 15 to 18 vehicles. It was not uncommon to see as many as five or six different units being deployed together, In Iraq they had the 518th Gun Truck Plt. They were a National Guard unit from Texas who called themselves the Regulators. They have a distinctive logo painted on the doors of the convoy security vehicles. I am building a few of their gun trucks now for a presentation this summer in honor of the crews.

Thanks Dave. Were would I find the demensions of the guntrucks for scratchbuilding purposes.

Let me know which truck you have in mind and I can help you out. If you have a AFV Club 2 1/2 ton kits or the 923/5 series Kit by Italeri You can make many different versions of the gun trucks. Either Vietnam or OIF era. Go to my gallery here in Armorama or at my web page at Webshots fora look at some of the trucks.
http://community.webshots.com/user/gtadw
http://photos.kitmaker.net/showgallery.php/cat/12306