If you go with the 3 speed get one out of an xl as it comes stock with the high speed 3rd already installed. Like said above slowly acclerate and listen for the shift. You want it to shift at the top of your motors power band (Not max rpm) to get the best proformance out of your truck.

If you get your shift points right it is not very noticable as it will stay in the motor's power band when shifting. You will hear the shift but it rev right back up almost instantly and even cause your truck to wheely when it shifts.