The spec number on the CH20 will determine how it was setup. With a picture we can give a little beter idea of what the engine might take to get it into the Cub. I'm not real familiar with the exact size of a command so I can't say for sure but it might require the removal of the side tins to ft it in. As far as hooking it up to the tractor itself, anything is possible with enough fabrication. Just depends how wild you want to get with it.
Post a picture or two of the CH20 from both the crankshaft side and the flywheel side so we can get a look at it. Also the spec number or a picture of the tag. As far as rotation, Cub Cadets ran the transmission from the flywheel side and the pto from the crankshaft side of the engine.