I have a 4" lift on my 1-ton pick-up, and after measuring the steering knuckle arm to pitman arm height difference, it was 3". At first I used a 4" drop drag link, but the dropped drag link over corrected my steering angle by 1", which may be causing my truck to not handle as good as it could.
Many people here say dropped drag links suck, and have recommended I go with a dropped pitman arm and factory drag link instead. I recently purchased a 2" dropped pitman arm and factory drag link. With a 3" difference, that will leave a 1" under correction difference, which I hope will handle better than having a 1" over correction.