That is interesting, the Bobcats of that vintage we had in the company had Wisconsin engine but those had the drive pulley right on the end of crankshaft, not on a separate right angle drive.Case did years ago. Probably made by Bobcat.....?? See below.
https://partstore.casece.com/us/parts-search.html#epc::mr54964ar292904
Well the snowmobile guys probably stole the idea from Vespa as that is how they were built and right up to today still are built. Wife has one I'm going to be replacing the belt on in the next couple days.Snowmobiles used 'em, too. Likely that's where the idea came from...
A friend has an old, early 70's I think, Owatonna skid steer and it has the vari speed drive.
Mike