I'm running 4.62's with 31's and they work well. I want to go down to 4.1 or lower in the transfercase just so I can crawl better.
I would look at trailtoughs hybrid axle for the rear I have one in mine and works great.
quoted from trailtough
Our no-hassle ready to bolt-in gear change package includes 4.62 or 5.12 Sidekick ring and pinion gears set up and installed in a Samurai front housing, a matching Sidekick rear 3rd member with drilled flanges for the Samurai drive line, and our Hybrid axle housing. Shock mounts, diff caps, SPOA perches, and Lockers are not included but can be purchased separately and installed at no extra charge.
Item #GCP-400 Price $749.00
Core charges $75.00 for front 3rd member
and $75.00 for stock rear housing