Back to how long.....
How long did you say your ram is.... Like 120+? I'm 102" and wish it was longer. I'dike to be 110ish ... Some of the other stretched bruggys I have wheeled with fall between that 108 and 112 mark and its amazing the difference (not to mention they all run sticky tires too). KB's rigs are all longer like in the 120 range.
Without doing some body work stretching, 106-108 is going to be your max by just pushing axles out. I moved rear only 10" back and may have another inch or two before it would be outside of my bumper. Consider in the rear losing your tail light housing to go that far though which led me to narrowing the tailgate and ending up with my unusual rear quarters. Also when you go to moving the rear you'll lose that under bed fuel tank space. I know you want a back seat so you'll have to get creative with space for a fuel cell, back seat, and tool storage.
One of my biggest regrets is not moving the front forward. One of my upgrades will be moving it 6-8" forward and full hydro, but that might make the tires stuck past the bumper which will create some major grill and fender trimming.