I run 5.12 gears and a 6.5:1 t-case, works great in low range with 33x12.5" tires. My next set will be some 35" while the 33's will probably find their way onto another vehicle.
My only issue is a lack of speed in high range. With the 4 speed I am limited to 55 on a straight, just don't have the RPM's to go any faster. I would recommend the 6:1 or 6.5:1 as a start, see how you like it. Then drop down to the 5.12 if needed.
What I think would probably work best is a 4:1, 5.12 gears and a Kicker 3 or Shogun setup with a 1.6L. Probably an 8 valve just to avoid wiring and go with a side draft.