Here’s how this will mount up. The motor’s an outrunner, so you mount the “back” of it, shown on the right, and for high-load application they suggest supporting the outside of the output shaft. This drawing also shows the standard output shaft. (This is the drawing for the smaller motor, not the 268 – note to self.)
There are several available, including a dual-motor shaft assembly, as well as an adapter shaft for an Audi. (!!!) Lemmee see. Running a motor that would work for a car, in a motorcycle? Sounds about right.