From the parts lookup
Ref:
IH-62383-C91
Tiller Front Drive Service | -Required to mount on 86, 108, 109, 128, 129, 149, 169, 800, 1000, 1200, 1250, 1450, 1650- -400,000 & above- -Replaces P/N IH-55032-C91
I do not have the time right now, but it would be a good study to pull up the drive parts breakdown for the tiller (noted above) and compare part numbers of the components to the same for the deck mule drive.
I am sure they both contain some of the same, BUT NOT ALL of the same parts. Would be interesting to note just which ones are different though.