That reference is crap for rear end lengths and is loaded with bullshit info. If you EVER see a chart or reference that says 62-70 B rears are the same length or track... IT'S WRONG!!!
Just a sampling of the BS in that reference from above...
Really all those models had 8.75's LMAO.
Here's a reference with good valid info regarding 8.75 housing, overall and axle lengths.
http://www.moparts.org/Tech/Archive/axle/16.html