Vanishing Point has some tanks with working treads, but I don't see an M1.  There is an M1 here, but it doesn't look like it has working treads.

http://www.forender.com/other_props/m1a2

Possibly the M1 model treads could be converted to work properly.    Here's the link where VK explains the process:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=1499769&page=1

===========================sigline======================================================

Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.