If you plan on just pulling this one time, and don't plan on replacing the stock clutch, then 4low 3rd gear is going to be your best bet. That and a good 100hp programmer or box is all you will need. I would get a Smarty 6.7. Make a set of rear suspension blocks between the axl and the frame and go have fun. 4low 4th gear or 4hi second gear would be better, but the stock clutch isn't going to hold up to that and niether will a big single disk. If you plan on pulling alot with it, go ahead and put a double disk in it, add a wieght rack, traction bars, and suspension blocks for the rear. You will also want to stud the head and get some gauges. BUt if its a one time thing, you will not need all of that, though 3rd gear low range, your probably aren't going to get up enough wheel speed to be very competitive, unless everybody else in the class does the same thing.