I spent this evening modeling the wheel motors mounts in Tinkercad. Yes I know there are better tools, but I like Tinkercad, it' s simplicity stops me from getting distracted.
The motors are going to have to be mounted upside down due to the fact the body of the car is going to be in the way if they are mounted the right way up. I'm using 1306 - 3000 motors with 16A ESC's and I'm hiding as much of the motor as I can inside the tire. I was originally planning on using 4-inch props but the wheel motor mounts would have to be modeled in such a way that it would look out of scale. Instead, I'm going to cut 5-inch props down to 3 1/2 inch props.
Once printed the wheel motors mounts should just push straight onto the frame and a few bolts will keep them in place.