For the tap you need 6". MSC calls them a "pulley tap". I bought one off of e-bay for less than $20 shipped last year, well worth it, makes the job way easier.
Are you just chasing the existing threads, or are you making new ones? If so how many turns after bottoming?
Hope you can push your truck a little harder now.
It definitely takes a while but is well worth it in the long run. I have done a few sets, and after each one I am always sore for at least a day or two.