I've tuned by adding preload/shock changes and using a scale. The final test may always need adjustment from the scale readings. If the weight is still in the range shown no wonder it goes right. The left rear is 130 lbs heavier than the right. It would benefit moving weight to the right. If that's not possible in my opinion it needs more than a 1/4 turn. I usually count the flats on the adjuster. My bet is it'll take 3-5. Start at 2 and work your way up. The ladder bar in itself works as an anti-roll bar unlike a 4 link. If there is very little flex it won't need one. All depends on how stiff the chassis, housing, and bars are. Mine is stock frame rail with no ARB with 3-4 flats of preload (every car is different). Dead level,1.25-1.27 foot brake. This picture tire is 13.5 psi
Doug