4" vs. 4.5" bolt pattern

OK I have a 70 Dart with 9in drums, (don't worry I'm replacing them with disks), but I don't know where to measure to determine if it is a 4" or 4.5" bolt pattern. Any advise on how to measure the bolts or at least where to measure to and from.

:snakeman:


http://www.wheelvintiques.com/pdfs/wheel_fitment.pdf




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