I could be wrong but some gear boxes are built so that the gear for the output shaft can be removed and put back in on the other side of the box. Other than that, the gear box may be able to be turned to the other side of the tiller. If the splines on the input and output shaft are the same, looking down at the top of the gear box just rotate it 90 degrees and move all the driven stuff to the other side. Depending on the diameter of the brush the speed may be OK. I have a 38" craftsman wheel driven sweeper. It does have a few flaws but generally works very good.