The M-37 was constantly upgraded. MWOs came out all the time. Some were mandatory some were as time/budget allows.
For example,
MWO ORD G741-W7, 3/4-ton 4X4 Cargo Truck M37: Relocating Spare Wheel Carrier, dated 20 February 1956, states in paragraph 4. that this work order is classified as URGENT and will be accomplished IMMEDIATELY on ALL ITEMS both in the depot and in the field.
So, from 20 February 1956 ALL M-37 were supposed to have the door mounted spare. The door mounted spare is used by some people to identify a B1 version. The MWO says otherwise. ALL M-37s are to have the door mounted spare. So, unless your M-37 was surplussed out prior to 20 February 1956 it MUST have a door mounted spare to be "correct".
The upshot being that the hood handle is the same thing. I think the marines started it but I don't know. There is an MWO for it somewhere however, because I've seen it; I just don't have a copy of it.
The M-37 was to be CONTINUOUSLY upgraded. Ideally, all M-37 would be identical throughout the army (or the marines, or navy or air force) REGARDLESS of production date. So, variations were the failure (or lag) in the system. Variations were a "flaw" not a "feature".
52 M-42