I dropped my front hanger 2.5" from stock, 3/4" forward (plus 2" forward fromt the rear spring swap - 2.75" overall) and I found that a 3.5" longer than stock shackle worked well (7" overall). I had tried running a 2" longer shackle and had bad death wobble problems. So as Harry mentions, as much longer as the drop, perhaps a bit longer, mine are 1" longer than the drop hanger, the AllPro's are 1/2" longer than the drop hanger:

Front drop spring hanger

Wide body front spring shackles

r.c.brown@ieee.org
TruckEditor@tlca.org
Project: 4Crawler
4Crawler OffRoad - 4x4Wire discount code