silly putty works great for locking the diff. i personally like to use just really thick grease, but that will work too for completely locking it out. Stampede tires are noticably larger then the Rustler ones, but they have horrible tread. IMO, if you're really looking for the larger tires look I'd go with some moabs or masher 2000's. it will require no work, have great traction, and not weigh the truck down too much or put too much strain on the motor. Although the maxx tires is a cool idea, I think it's a bit too much. At that point you lose the Rustlers handling and what was a zippy truck has now turned into almost a truggy?