Great photos, George!
All the halftrack mounted versions are M16 Machine Gun Motor Carriges… the White version, identifiable by the “automobile” type shaped front fenders. The International Harvester halftracks (M5, M17, etc.) had “flat” fenders without the nice double curves of the Whites.
Your pics also show the difference between the early and late M16s… the early models had special rear armor, with fold down flaps at the top edges to allow the quad mount to traverse. Later models had a riser to raise to machine gun turret, and were able to use the standard rear armor. M16’s used in Korea, had added “wing” armor on either side of the turret to protect the ammo loaders.
My dad was a member of an AAA unit (90mm), interestingly, the 45th AAA Bn, during his time in the Army (1951 - 1953). He was NCOIC of a section (3) of deuce and a half mounted M45’s (to protect the bigger guns).
Russ
Proud son of Rose and Wes