So, I'm trying to determine which of the two different width 1970 C10 rear ends I have. I've been told that if I measure from backing plate to backing plate and it's 55.5" then it is the older 67-69 version and if it's 57" it's the 71-72 version. Well, I'm still not sure where to measure from. So here's a pic. Should I be measuring from spot #1 or spot #2 (or somewhere else entirely)?
