Okay, newbie Jeep owner here, 95 ZJ, 318 V-8, disc brakes all around. I'm an old school 4 wheeler, had a Scout, Blazer, F-seies trucks. The ZJ is a daily driver, want a little more off-road capability for construction sites and not-so-serious trail riding. I don't generally thrash my rides. Well, sometimes, lol. Also, I haul a 3000 lb. trailer a couple of times a week. SOOOOO..... Opinions, please.
Biggest tires to run with stock suspension?
Is a 2 or 3" lift worth it? Which brand? Should I put air bags or something in to level the Jeep with the trailer?
My transfer case (not sure of the model) has 4WH/N/4WL. Can/should I swap it for one that has a 2WD position? If I do, would manual hubs make sense?
How would the proposed mods affect gas mileage? I make a 500 mile round trip at least 2 weekends out of the month, all highway driving.
Will putting larger tires on create any problems with the computer system?
Thanks for your input, I'm sure I'll have more questions later.

Just thought of one more. I can't use my hi-lift jack with the stock bumpers. Suggestions for aftermarket fornt and rear? Should I have them fabricated out of steel channel or something?

I'd say airbags rear, bags or coil spacers front. make sure youve got skid plates, if not get them, they were optional.

there are (or were) some nice aftermaket bumpers out there for the ZJ, but they are pricy.

playing with the transfere case and hubs may save a miniscule amount of fuel, but it'll never pay back the upfront costs.

I'd stick with near stock size tires, but something more agressive. that way you don't have to mess with gearing.

winch is always an option, that way you can get over your head without it being catastrafic.

I suspected as much re:transfer case & hubs. My F-250 lunched the axle splines when the automatic hubs went south, so they got swapped for Warns,and I converted the Blazer to part-time. The Scout was pretty primitive, but as solid as a hammer. Hence my wondering. I was hoping to be able to use some of my collection of truck tires, 31-10.50-15s, not sure about clearances, and don't want to overload the axles, but would like a little more clearance at the axles.  
I've seen the ARB front bumpers, but $800 is a lot to spend. Haven't seen rear units, but I'll keep looking. Kinda like the idea of fabbing my own.
Regarding the winch: I always see them on the front, almost makes more sense to me to have them in the back so I'm not just pulling myself deeper into trouble!
BTW, on the long highway trips, I've averaged anywhere from 17 to 20 mpg, depending on how much of a hurry I'm in.

you'll need some lift for 31s on a ZJ your axles will be fine (if that aluminum D44 in back isn't making noise already). get a multi mount winch (goes into the reciever) for front or rear and it doesn't suck gas on the highway. I believe the big companys make front hitches for you. the only problem is the rear hitch isn't made for much side load, its made for towing.  

Look for a nice coil spacer lift kit. Look for one with shocks included in it. I have a coil spacer kit that netted about 1 3/4" lift and i can run 31's on my 93 ZJ. If i were to redo it, i might have gone with some thing along the lines of a 3" kit and some 32's maybe. ARB does make a front bumper and you pay for the quality. I have found them for around $650-$700. You can find some from Kevins off road and also Protofab i believe. Both offer a tube style bumper. As for making your own...Yea it will be a little difficult as the front dont offer much in the way for mounting locations since its a all unibody construction. I  tow a small trailer with 2 dirt bikes and my riding gear and i dont have much a problem with the rear end sagging down on me. If you go the spacer lift and 31's route, just check the top of the tire to fender clearance in the back, as some times i rub with the rims i have on mine when i put a lotta heavy items in the rear of my ZJ. I know Trail Ready is another company that makes a rear bumper and front bumper for the ZJ. I personally like the look of the ARB the best. Its Air Bag compatible also, so it wont mess that up if ya still have it working. I dont know about a hitch mount for the front but you can look around for that. Just do some searching, and research before you buy. learn from the mistakes and opinions of us ZJ owners out here. There are a few of us on here.  Good luck.  

I have a Tuff Country 3.5 inch lift. I also have their shocks. It's cheap and works great. But their shocks rust out faster then I'd like so next time I'm going with a power coated shock or paint their shocks with a rust paint before i install them for added protection. Also Look into Rusty'soffroad.com they have nice 3" lift there for a good price as well.  

Let us know how you made out?