Originally posted by TimG
Edit: Well not to run each trail, the min specs to run a 4 rated trail.
It depends on the trail.

Like Pritchett Canyon for example:
Front AND rear lockers required.
Minimum 35" tires
Low gears and winch HIGHLY reccommended

Golden Spike
Rear Locker and 33" tires required

For most other trails in the 4 range, the following is reccommended:
Rear traction aid, locker preferred, but a LSD will work
Some lift to accomodate slightly larger tires 31-33
Rocker protection

Those are minimum guidelines, and are up to the individual trail leader, and trailmasters whether or not you have:
A) Proper equipment
B) Sufficient experience
C) Trail availability

Hopefully that helps to clear up some of the issues.