Very cool, I had always thought that was a very interesting machine. I would ask TimT he had posted a few pictures a few years back. There isn't much that I have been able to find on the internet although I do know that there is information about it in the book The Caterpillar Century and Super-Duty Earthmovers both by Eric C. Orlemann. Here is a little info from Super-Duty Earthmovers.

"In October 1965, Caterpillar introduced a massive,240-ton capacity prototype bottom-dump coal hauler, Designated the 786. At the time, it was the largest type of hauler ever constructed by an manufacturer. The Cat 786 was in the same family of electric-drive-haulers as the 779 and 783. The same Cat D348, V-12 diesel engine was used in all of these trucks, but the 786 had two engines, one at each end, driving the leading axles through a Caterpillar-designed electric-drive system. The power ratings were 2,000 gross hp and 1,920 fhp. Only four Cat 786 coal haulers were built in this configuration. The pilot version had the engines mounted on top of the tractors, not in front. All five units worked at the southwestern Illinois Coal Corporation's Captain Mine (now owned by Arch Minerals) in southern Illinois. The 786 was 96 feet in length, and weighed in fully loaded at 670,000 pounds. After 1969, all work on the electric-drive hauler programs by Caterpillar ended. These incredible haulers were soon relegated to the Captain Mine's bone-yard, and scrapped by the mid-1980's. ECO Collection"


Hope that helps a little.


-Josh

It doesn't look like much info out there on this monster truck. But I still plan to build it this winter.