[QUOTE=C-Bag;95469] . . . The stumbling block for me is the two spur gears. QUOTE]

A couple of circle car Quick Change spur gears will work. They are cheap and available from Sumitt, Jegs, Speedway, etc. The only hang up is they are internally 10 splined. But a keyway and some ingenuity should do the trick. You could even have different ratios (i.e., speeds for different jobs) if so inclined. :-)