The reason for lift is to make room for bigger tires. Bigger tires take a lot more power to turn and you cannot beef up your engine enough to compensate. The only thing you can do to gain more power to the wheels is change axle gears and you need to know what size tires you're going to have so you know what gear ratio to get. 6" of lift will require more modifications than you can imagine. IMO just save your money and go with 3 or 4 inches of lift, 33 inch tires, and 4:56 gears (manual tranny).
D30 w/powertrax no-slip,D35 w/ultimate 35 upgrade OX locker,4.56 gears,Air on Board, Mile Marker Winch
Warn Lockout Hubs