Then Id suggest some weights or maybe some less agressive tread pattern tires. Shes Still a work in progress as I'm tuning it in for 100+MPH runs but right now the weight distribution is off...I'm still trying to figure out something that works better. I think the best speed I've managed so far without crashing is about 86MPH. can't run it when its cool/cold outside as the tires dont grab enough traction and the kit is brittle if its to cold. I'll resume my quest on it this spring when it gets nice and warm.
You have to buy a transmission case with a flat aluminum motor mount to get it to fit and you have to dremel out the lower screw hole where it slides especially if you start putting large pinions on it like I have.