It actually depends on the 37's you choose, some run bigger than 37 and some run smaller. The ones that run bigger will for sure give a 6" lift problems and I believe it will take more than a heat gun and pliers. I've done a couple experiments with lift on lift and I'm not sure if a 2" coil pacer will work with a ProComp 6" but it might be worth looking into. If it does look into a Deaver 2" rear leaf set up to level it.
New Products Just a thought.