Imagine this. Your SGT boss tells you to mount a radio in your contact truck, and he doesnt care hpw. Your a SPC, and want to go home on time that day... You do whats easiest for you, while still accomplishing the mission. Usually, my guys put the radio and antenna on the pass side, with the thinking they set the drivers side up for the "most likely to be used" tools/parts/stuff. The passenger side was kinda for "less likely to be used" stuff, as you need to remember the mission of a contact maintaince truck is to fix/repair/replace forward, possibly under combat condtions with the bad guys not too far away... We're not talking swap out engines kind of stuff far forward on the battlefield. That sort of stuff happens farther back in the TFSA where "bigger" wrenching occurs.
Bottom line, either side is fine, but all of mine were on the pass side front for whatever reason. That being said, the next motorpool over had theirs mounted on the rear pass side. The radio was set on the CO net while on mission, and they rarely needed to change channels.
Just dont throw 5 gallon pails of 80/90 weight on top of the radio set, when the top comes off, it makes a HUGE mess out of the radio set/amp/mount... It took that guy a LONG time to clean that up.