Love the 4 banger in the 2nd picture.
Both of those mules are "4 bangers". Is that not a muffler on the starboard side, at rear, just in front of the marine's left knee?
Picture #2 was portrayed as a "A5" in Denise Moss', article in MV magazine and also in David Doyle's MV ID book.
Both of those mules are either M274 or M274A1, Carrier,Light Weapons, Infantry. Both have two mufflers, only the 4 cyclinder engines had two mufflers. The 2 cyclinder engines (A3,A4, and A5) had one muffler on the port side, under the air cleaner assy.
When the Army used the mule as a TOW platform, they used the M274A3, A4, and A5, all with the upgrade kit (wide wheels, electric start, fenders,etc.). But not all mules with the upgrade kit had the TOW mount.