I have now acquired a snowblower for a 3600, From the look of it, the frame looks the same, just pulleys added for the the 6800. The big difference is the 3600's use a drive shaft, so that would take some engineering, The 3600 is smaller as well. The one I got needed a new drive shaft, after allot of digging and trips to the different drive shaft makers, I ended up with a John Deere drive shaft, will need some machine work, but it has the quick connect and is beefier. A Gravelly shaft will also work. These shafts are expensive!
3-YT3600's, 2-YT 6800's, 1-YT6700 for parts.