In my previous projects, I purchased metal brackets to mount the motors. I considered designing my own bracket for 3d printing, but I usually search thingiverse.com first and I found a great bracket here:

Print two of these brackets.

Mount the motors to the brackets using M3 x 6 machine screws.

Solder a .1 microfarad capacitor across the motor leads.

Mount the motors to the body using machine screws and nuts.

Route the wires through the hole to the back of the assembly.

Print two wheels (at least 50% infill) and push the Eureka vacuum belts (tires) onto the wheels.

Push the wheels (friction fit) onto the axles.