I might could help with a small part of your question. I have my upper arms raised 2", i realize its an older truck than yours but same principal. I have 22s, I used the ektensive metal works kit to do this. I think some people do 3" cause of larger wheels. You dont have to I dont think but you get crazy camber if you dont. If it were me I would email all of those questions to Ektensive
http://www.ekstensive.com or even call. They are not only extremely knowledgeable so you'll for sure get an answer you can rely on, but they are some of the coolest and most helpful guys out there.