The University of Arkansas ag experiment station had a few of those when I was a teenager working there back in the early 90's. They had 3-4 of them IIRC and usually only had one running at any given time.
Last time i saw they were sitting back with the old equipment rotting away.
As with all government BS, they could not sell them without sending them to state surplus to be auctioned off, and when they do that they don't get any of the money for the auctioned off equipment, so the stuff just sits there and rots.
They have a couple of M416 trailers sitting out there too. I've asked a few times about buying the mules and the M416's. Always get the same canned response.