I think you need to move the spring hanger forward. The angle your shackles are at now is where they should be after they settle. Once theydo settle the rear is gonna sag. Try moving the s/h forwad a half inch at a time using tackwelds. Also i don't know if the stock spring perch has the three different holes like the aftermarket ones or not but try using the rear most slot.trial n error my friend.
