I followed TG's instructions for setting up the springs for a truck w/ the v6. They suggested pushing the front cross member forward and centering the shackle mount between the body mount. Doing this was good for lift but not good for taking advantage of possible suspension travel. I do like having the front hanger forward b/c it helps keep the tires out of the fire wall, I’m running 37's. So what I decided to do was keep the front hanger where it is (b/c it would be a bitch to move and i like the axle further forward) and move the shackle mounts forward and lower on the frame. Basically I measured the top leaf spring when it's flat, which was 48". Then measured from the center of the front hanger bolt hole back 48" to a point about 1 inch off the frame. From that point I measure 5" (that is the length of my shackles bolt holes) forward at an angle to a point on the frame where I could put the shackle tube. This way I can use all the potential travel of the leaf spring and this will give me a lower stance. I’m sure I’ll be doing some fender trimming.
I'll try and get some pics this weekend, hope this helps.