I'm putting a bronco rear end in model a chassis. The factory spring was to wide for my rearend it was in the way of backing plates. I ordered a brand new main leaf that is 2 inches narrower on each side. So a total . In theory do I just move the spring perches in two Inches also or do u think that new spring being shorter and stronger it may vary. I took the main spring apart and it's right at 4 inch total compared to old spring. Or is there another way to make sure the perches are where I need em.