There are a few guys on here running 37's on just a leveling kit with no rubbing. You can run them with your 4" lift. The issue isn't as much the lift as it is the width of the tire and offset of the wheels.
If your 4" lift included a pitman arm, you should be able to add a 2" spring spacer (leveling kit) to the front and then change shocks. If not you may be able to also add a pitman arm from a 6" lift kit. Not knowing exactly what lift you have makes it all a guess.
What you do out back will depend on what your 4" lift included. First, your 4" lift probably only had about 2-1/2" in the rear. They do that to level the stance a little. If it was raised by a block I would not recomend a taller block, 3" block is the most I would run personally and people generally say 4" blocks are the limit and you should use traction bars if you go that high on just blocks. If your 4" lift used new rear springs or an add-a-leaf you should have no problem installing a block for 2" higher.