If you've decided to build for off-road adventures and leave extreme wheeling in monster boulders and bottomless bogs to the purpose-built buggies and pond trucks, then you've come to the right place. Think "everything in moderation." First and foremost, a trail rig needs to be reliable or at least self-sufficient. Ultimately, building a stout, reliable Jeep is easier than carrying a spare for every component on your rig. Your trail/adventure Jeep should be built to conquer mud, rocks, dirt, sand, logs, and anything else that may get in your path--even the street. Aside from keeping a full set of tools, recovery gear, and supplies in your adventure Jeep, these are the top spots that need some attention.
Jeep type: Just about any Jeep makes a good trial rig. Base your choice on the kind of terrain you plan to adventure in. If tight, wooded, or rocky areas are in your future, avoid longer, larger models. If high-speed, wide-open, and bumpy roads are more your forte, then stay away from wheelbases shorter than 100 inches. The rougher and tighter it is, the less body metal you should have.
Components: Stick with easy-to-find, OE-type components when it comes to fuel pumps, ignitions, engine control systems, and so on. Avoid using overly high-zoot race parts because they're often not as durable in the adverse conditions a Jeep sees. Plan for the worst. If a parts store has the component you want in stock, then chances are it'll be easy to find just about anywhere when you're stranded in the sticks--special-order parts mean you're camping or staying in a hotel a few days. If you absolutely have to run a high-end, hard-to-find part, consider carrying a spare.
Tires and wheels: Even for average wheeling, we'll typically choose a more aggressive mud-style tire, no matter what the size. Any bit of mud will often clog the tread of all-terrain tires, rendering them practically useless. Look for a good name-brand radial with at least three sidewall plies. Carry a fullsize spare, maybe even two, if you have the space and plan for long trips in the outback or Mexico. Stay away from overly wide tire and wheel combinations. We're fond of 8-10-inch-wide aluminum wheels for weight savings. Less weight and width translates into less stress on suspensions, steering, axles, and the rest of the drivetrain. Optimal trail air pressure will be dependent on terrain, speed, tire size, tire construction, and the weight of your Jeep. For most areas, air down until you end up with a nice bulge in the tire. Typically, this will be in the 10-15-psi range; you get better traction and a smoother ride. If it's overly rocky and you're moving at speeds, you may want to air up just a bit to protect the tires from punctures.
Suspension: Look for shorter, quality, complete lift kits. Thicker leaf-spring packs with more thin leaves are preferred over thinner packs with fewer thick individual leaves. The thin-leaf packs will provide a better ride. Does your Jeep have round springs? Pony up for progressive-rate coils, which will smooth bumps better than standard lift coils. In some cases, the stock coils will ride best, so you may only need a small spacer to fit the tires you want. If off-road speeds above 15-20 mph over long distances are expected, you should move into a monotube shock, preferably with a reservoir. These will help dissipate heat better and will not fade as easily as some other shocks. Install properly located bumpstops to help keep the tires out of the fenders and the suspension from overcompressing. Set up the suspension so it has about equal amounts of up and down travel.
Drivetrain: In most cases, the stock drivetrain will work fine for average trail use as long as tire size and speed are kept reasonable. Reckless high speeds in overly rough terrain and vehicle airtime could bend axlehousings. A good geardriven rear limited-slip will get you just about anywhere, and a rear locker will be more than enough in most cases. Even stock axle ratios with oversize tires can be made to work effectively. Automatic Jeeps should be fitted with a large cooler plumbed inline after the factory internal radiator cooler. Use Low range whenever your speed allows--the extra gearing helps keep auto trannies cool and alive. Stay on top of fluid leaks and other problems. The last place you want them to get worse is in the middle of nowhere.