jeep wandering problems

i have a 76 cj5. 6 inch shackle lift, 3 inch body lift, 35 inch tires. replaced steering box, checked all joints (tie rod ends, ect.). It wanders down the road at any speed above 10-15 mph. ive run out of ideas that could cause this. could having 6 inch shackles be causing to much positive caster? any help would be appreciated. Also, addition of steering stabilizer had no effect or change on problem.