Hi Matt,
Welcome to the forum.
Your 'Machine Gun Carrier' was built by SAR as an LP2, and was originally registered under the Uniform Commonwealth Registration scheme as C-22033. On 26 May 1942, the registration was changed to the hull number '316'. It was originally built with a 1938 rear axle with the splined pinion and a ratio of 6.66 to 1 (marked 6-40 on the casing). It is the rear axle assembly that denotes the difference between the LP2 and the LP2A: the LP2A having a 1940 type rear axle with a tapered pinion and woodruf key.
First engine fitted to Hull 316 was engine number 1G4992F.
Army inspectors accepted carriers from SAR around hull number 310 in April 1941, so I suggest your carrier was received by the Army in April/early May 1941. It was manufactured as part of MGO Order Number 698 issued in August 1940.
Your second carrier donor hull: As Keith said, check the flat horizontal strap on the inside face of the rear hull plate, just above the aperture that the diff protrudes through. On that should be stamped the manufacturing plant and the hull number of your second carrier. As Rick said, the tools on that one are across the rear, so most likely to be an LP2A manufactured with a hull number higher than about 2700, however, this is not definitive, as tool stowage on some earlier carriers was also moved to the later position as a modification. Most earlier carriers, however, were left in their original configuration, so I suggest that Hull 316 would probably have been that way when it came out of service.
At least you have some good private examples close at hand to look at. Pity access to AMB is not available at the moment, though.
You'll be attending Corowa, I assume, for a real MV initiation, and you can put faces to some of the
nom de plumes we use here!!!
Mike C