These are the gears as I understand them.
R51 RWD - 3.13
R51 4x4 - 3.36
R51 V8 - 2.94
So as long as its 4x4 it sould have the highest gear ratio.
I would be very surprised is the brakes weren't identical between all trim levels.
Also, don't let IRS foul into thinking its not offroad capable. Outside the US, the R51 is a pretty popular trail rig. Granted it won't do the Rubicon in stock form, but it will get some surprising places.
This is a 7 part video of a guy taking a lifted R51 up Wheeler Lake