Finally after some cutting, drilling, tapping, filing, "dremeling", sanding and many other words i don't know, i got the motor mount done! I am pretty pleased with it, and the way i solved the challenge of making it adjustable for different sized pinions in an easy way. Maybe not a beauty, but will still do what it is designed for.

The little slot i have filed out on the bottom is to get it close to the diff mount marked with a red arrow in the chassi picture. This allows me to put a screw through the mount (the countersunk hole) to secure it to the diff mount and into the hole where the brake pads used to be.