A while back I bought the Old Glory African Pick Up Crew with HMG pack, but hesitated to mount the MG and gunner in my pick-ups, as I also needed them as transports for my games. So I ended up mounting them on styrene plastic bases, cut to fit in the beds of the pick-ups. I had minor concern that they would tend to fall out of the trucks during movement, but they turned out to be pretty stable.
The bases were cut to allow the gun to face forwards or to the rear, and allow the machine guns to be used independent of the trucks in static positions such as bunkers and whatnot.
Eventually I will buy a few more pick-ups and light vehicles and make a some more dedicated technicals, but in the mean time, these give me a little greater flexibility when using the pick-ups.