Here is a shot of the motor with the mounting plate bolted up:
https://postimg.org/image/q8kgagrad/]
[/url]
Although the drive motor has a D-shaped pinion shaft the pinion doesn't have same D-shape. The pinion is a press fit more or less and does not have a set screw.
On the plus side the transmission had plenty of grease in it and operated smoothly.
Here is a pic of the motor\transmission assembly:
https://postimg.org/image/3wmnh1plh/]
[/url]