unfortunitly you already have the lowest r&p gears for the kicks (5.12) you might be able to source some 5.62's (very rare stock gears) or maybe some 5.83's (calmini, out of production)
transfer case gears wont do anything for 2wd use so it wont help with driving down the road.
either swap in an automatic to compinsate (they run 4.56 or 4.88, cant remember exactly) and with the 5.12 r&p 31's would turn better.
or fab up a samurai transfercase doubler on it. (makes you good for 35's)
this is the reason so few guys run 31's on the street. theres no real way of getting it regeared.