Anyone know what the differences were in the .50 cal MG mounts? I've seen them on the back of the turret, some in front of the commanders hatch. Does the cupola rotate? Any help would be greatly appreciated. Thanks!

Gday Haodoken and welcome!
Yes, the split hatch rotated, but the later cupola with the vision ports did not... Only the inner rim of the cupola single hatch rotated through 360 degrees for periscope use when buttoned up...
The split hatch had the .50 cal mount on the ring itself... The pintle mount on the turret was introduced for the later cupola. It could be unbolted and folded over when not in use...
The 105mm had it positioned to the rear in a bracket over the additional vent...
Hope this helps some
Cheers
Brad

In addition to what Bradley mentioned, sometimes crews would mount extra MGs as it suited them (think of Thunderbolt VII, Creighton Abrams tank -- it had an extra .30cal MG mounted on the gunner's periscope armored housing -- Abrams must have wanted the extra punch for himself)

Thanks Guys! That's what Info I was looking for!