Make sure he does the gov spring kit first. This will widen the powerband enough he may not need the splitter. I have both and find the governor kit makes for the biggest improvement. So far I'm not all that impressed with the extra driveline trash with the USGear. Only benifit I find is lower cruising rpm with my 4:11 rear. If I had 3. 45s I wouldn,t use he 2sp. Of course if he's trying to pull that big trailer with an auto he needs all the help he can get. :{