I haven't officially weighed it but here are some rough numbers. Front bumper 137lbs, skids 250lbs, winch 87lbs, roof rack 70lbs, aux fuel (6lbs/gal x 18gal = 108lbs + tank, skid, and mount 40lbs) 148lbs, rear bumper 150lbs, so throw in the lights, wiring, fridge, and awning and it's about 900-950lbs bring the estimated total to approximately 5,750lbs leaving 550 lbs for passengers and cargo. Keep in mind that the suspension and tire capacities have also increased, that is not to say that I have completely and thoroughly raised the rated GVWR, but I have taken compensating measures that are most directly impacted.
Mileage overall is about 13-16 depending on conditions. I can now carry 41 usable gallons without stopping so say 14 x 41 = 574. I haven't been able to formally test yet so that is just an estimate.
Regarding the 4:56's, all of the above. Fast low range, poor power around town and big climbs, shift points seem sluggish.
Good questions.