Biggest issue is holding onto the naked DeWalt tranny. The leg between the motor and tranny is actually two pieces. One (1/4" Al) is the motor mount. The other is 3/8" and fully keyed (water cut) to fit the base of the tranny. I've got the DXF of the pattern if you go with something like it - saves weight - naked DeWalt is only 0.85 lbs.
We used 1/2" high-carbon keyed axles - machined 3/4" from one end to fit the 0.3 x 0.25 double-D tranny output. We found early on that unhardened shafts snapped. Heat treating solved that.