welcome to the fourms. i dont know if u want to design and build but a person by the name of dafni on here has a kit u can buy witch is a new chassis, center diff, and drive bones and all the other things so u will have the roller with everything u want to do cheaper, and it looks incredible i was going to buy one and then my track got mowed over so yeh lol and that speedy is good a 9 or 10 xl would be good