do you measure the top of backing plate to top of backing plate ?? I have 53 3100 got 59.5 for measurement,, reason I ask is a friend was gonna give me a 85 camero 10 bolt eaton posi rear (3:23) which if Im right is 56inces wide bp to bp, could this work with a 3inch offset rim?? Im asking cuz I dont want something that wont work..