5100s preload the stock coils in front to lift the front end. They don't lift the rear. Add a leafs or AAL is exactly what you are thinking. There are a few brands, alot of people go with the toytec
AAL but i have heard awesome reviews on the Icon
3 leaf progresive AAL. So you have 4 leafs, that means you have the TSB leafpack, keep that in mind when ordering an AAL if you go that route. Your truck already sits a little higher in the rear conpared to the stock non TSB leaf springs. Just to let you know bilstein 5100s with stock coils will make the front end stiffer. If you are concerned about ride quality some longer coils would help, toytec sells eibach coils for 1.6" of lift with the bilsteins set at 0. 883s by old man emu would probably yield about the same amount of lift and 884s would give you about 2-2.25" of lift up front.