X2 on the gearing comments earlier. If you're wanting to run a 37" tire in the mud your jeep will hate you if you're geared too tall. I would go 5:38's and never look back, which means axle swap of course. Who cares about highway MPG? It's an XJ for hell's sake. You said it's all about the mud, so gear it low and do once, do it right.
Other things to consider are driveline angles, SYE if you don't have one and shims in the rear/cut rotate the C's in the front for optimum angle, steering (which you mentioned) including beefing up the steering box area with plates/braces. And on 37" tires with lots of wheelspin in the mud, you'd be best off to stiffen the frame rails too. The unibody will take a beating if you don't.
It's an ambitious build, so yeah, more research is highly recommended. Good luck.
Other things to consider are driveline angles, SYE if you don't have one and shims in the rear/cut rotate the C's in the front for optimum angle, steering (which you mentioned) including beefing up the steering box area with plates/braces. And on 37" tires with lots of wheelspin in the mud, you'd be best off to stiffen the frame rails too. The unibody will take a beating if you don't.
It's an ambitious build, so yeah, more research is highly recommended. Good luck.