[Andy Brockway]

FP welds a bar onto a nonrotating shaft than runs through the output gear hole. This provides a shelf for the gearbox to rest on and prevents rotation.

In the past we have wanted the shaft to rotate so we rested the gearbox on a piece of aluminum angle, 2x2 x 1/4 thk, and transfered the hole from the gearbox. The hole will end up against the web of the angle. we then used clamp collars on both ends to prevent axial shift.

You will have to adapt this for your application.