I just finished lifting (RE 5.5 tri-link) my new Rubicon and installed 315/75R16 KM2's. What is the best approach to correct for the speedo error? The local dealership said that "they couldn't go as big as 35's" and they wanted $90 if they could.

superlift
or
Nevada speedometer.
you need a module that goes in line and manipulates the signal.

Havent played with a LJ, but do you not have a speedometer housing that bolts into the tailshaft of your T-case? Should be a little plastic gear in there...

Rubicon's dont have the gear, they are different. as said the truespeed. for mine 4.56 gears and 35 are dead on the speedo, and 4.88's with 37's are also dead on.