Ok....I'm going to put this down....
Can they? Yes.
Do you need a "turtle back" with a ring turret? No
During the battle of Fallujah, I was watching CNN and eating breakfast. I was seeing some of the footage of the street fighting and I almost choked to death with I saw an M998 with armor plates welded to the side of it. A twin mini-gun mount on a pintle bolted to the center of the bed, crewed by two marines. One of shoveling the brass out the back of the truck as they backed out into the street...the gunner hosed (I use this term because the guns did dance around a bit) and then pull back into the alley where they had cover. I never saw anything like it again. There is plenty of room for tons of ammo, and depending how close your ammo supply is to get more...you'll be good. But monster excessive? Maybe.
I do see them mounted on 1141 or 1151 armored HMMWVs. You can pretty much fill the whole trunk with ammo. Intelligent design of your ammo supply system is a must. If you don't have the sleeve that guides the chains into the weapon...yer screwed.