Jim,
The Rancho 4" lift is a full suspension lift.
I would not suggest any kind of a body lift, and never a body lift in conjunction with a suspension lift.
Rancho or Skyjacker are about the same...Come by and I will show you all the components on mine..
With a 4" lift, 37's just barely are big enough.
Travis
http://www.HummerTeam.com