Centering the rear wheels

I bought a 3/4 " spring relocation kit from Dr Diff. With offset rear shackles and a 1" lowering hole up front. I used Afco leaf springs, and didnt pay enough attention at the time. I got the springs with a 6.5/8" arch. And i should of gotten ones with a 4.2/5 arch. I also have a 1.5" lowering block in my duster now and the car sits where i want it too.