I would try to put on atleast 300 miles(or as much as possible) to break the gears/engine in, as well as some sitting in stop and go type traffic to make sure the engine cooling system is working correctly. After that I would change out the fluids.

Another thing you may want to consider is, did you change out the gears yourself, and how many times have you changed gears? If this is your first set, I would wait long enough to make sure the gears were set right, unless you are bringing an extra 3rd(or two). Sometimes if the gears are set close, but not right it takes a couple of 100 miles before they start making noise. A buddy of mine went through 3 sets of gears on his Ranger before he finally got them set right doing it himself.

If it were me, I would wait until I knew for sure that everything was installed and working right, before hitting the Rubicon. The Rubicon isn't a fun trail with a broken rig, even worse if you are having to be towed out due to a bad engine.