TIRES are the first ingrediant in clearance. I don't care how high you lift your vehicle, the axles are still gonna hang just as low on a stock vehicle as they are on a 12" lifted truck. Larger tires are the only way to raise that axle height. Once you've increased the tire size, you now need to regain proper distance between tire and fender/frame, this is accomplished via longer springs and or body lift.
*The following is my opinion/experience*
Uptravel (the distance the tire travels upwards before it hits the bumpstop or fender) while important, is NOT as important as downtravel or droop. Droop allows the axle to swing down and find ground when you are crawling over obstacles. ANYBRAND truck lifted 12" on mud tires parked at the mall may look cool (let's face it, we may make fun of it but inside many of us still think it kind of looks cool), but if those springs don't provide proper droop or downtravel, that truck will be as useless off road as a PowerWheel. Trucks with poor droop or bad spring load dont articulate their axle well when crawling, this often ends up shifting the vehicle's body left or right towards the low end of an obstacle and could lead to a flop or rollover. Sway bar disconnects allow the axle to swing down further and a set of longer travel shocks will provide a healthy amount of downtravel. In a perfect set-up in a perfect world, the vehicle would be able to traverse obstacles with the body level to the ground and the axles articulating to the proper degree. Control arms fitted with Johnny-Joints or other swivel/ball joint ends provide even better articulation of the axle while relieving stress on the components. Lower lifts coupled with larger tires do quite well as they provide proper fitment of the tires and proper downtravel while maintaining a low center of gravity. Stability is key not only when driving on the road but off road as well.
For most ppl who weekend wheel, the best all-around lift/tire size (for a jeep anyways) has often been quoted as the Rule of 3 or 3" and 33s. 33s are great on road and are large enough to take on most trails. 3" kits (at least the good ones) should provide plenty of suspension travel for the various obstacles the weekend wheeler may encounter. Keep in mind: STOCK vehicles have made it through the Rubicon trail. Now the rule can be modified a bit, for example a Jeep on 35s and 2.5" of lift can be even more capable than the aforementioned example as it provides a larger tire for clearance and a larger than stock spring for better travel, added clearance of course can always be gained with fitment of a body lift..
That's my 2 cents anyway
98 2.5l. 33"Toyo, OME 2.5"+ 1"Body,IronMan control arms, Currie/IronMan steering, Front Eaton locker, 8.8rear,4.56gears TO DO: Diesel Swap