[bronsonj]

Heck of a project!

I can't see your sketches or photos because most hosting sites are blocked by my employer so I can't help with that.

As far as speed goes, 35+mph is doable but is dramatically affected by your gearing. I'd go with an AC motor and controller. Navitas sells kits for that. The AC motors seem to have a higher max safe RPM. I guess they're banded to protect them from the centripetal forces.

To calculate speed you'll need to know the differential gear ratio and the tire diameter. You already know the transmission gear reduction. Then you can calculate the distance traveled in inches per revolution of the engine. Or you can see how many engine revolutions are required to rotate the tires one time and extrapolate. You know the length of a mile is 5,280 feet so you can calculate how many revolutions are required to travel that mile and divide by your max motor RPM.