When I was stationed at Ft. Lewis in the early 80's I came across a guy in Tacoma who had imported some Chinese bulldozers- they were actually tracked tractors. He was in the process of modifying one with a ROPS canopy and 6 way blade. Over the next few years they made a number of changes by lengthening the tracks and adding a reverser. They sold them under the name of Powertrack. I sort of lost touch after I was posted overseas, but I think he is the same guy who invented the 3 in 1 lathe - mill machines.