I started carving the gearbox out of a chunk of styrene when I realized I forgot to mention another critical part of the diorama - the trailer conversion dolly:
Pretty straight forward - I sacrificed the rear of the White cab from the Atlantis kit and added a few bits. I still have plenty of small details (such as brakes and plumbing) to add but you get the idea. It’ll have six hole military wheels on it once they arrive.