Thomas,I have a few F-350 tranys running a 10 tooth pinion.You have to grind the mounting holes bigger to drop the motor closer to the trany. Also have to cut top cover so motor can sit down in side of trany.
On this one I used a brushless,But it can be done with brush motor.
Just don't grind with trany together,remove end plate to do your butchin.
Or just run stock pinion.
Hope this helps!
FGD