Jonny, if your going to be pulling 8500 to 9000 Lb, I would for sure get the 3.55 gears and if your pulling it a lot at 4500 and higher
I would try to get the 3.73 gears. The Upfitter Switches (+125) you ask about are 4 switch's in your dash that you can add lights or
other things to, myself I...