Yup, that's a great wiring diagram. Although you might notice it doesn't tell you that the red green wire changes to black at the disconnect.
I'm currently rewiring that part of my 67 mustang, so it's all pretty fresh in my memory. If your getting 8 volts at the black wire while the key is in the run position, and 12 volts while cranking, congratulations. You have a correctly wired stock setup.
Stop what your doing and read up on the evil pink wire

Conduct a search on this forum for "pink wire" and you will find dozens of people who have been in your situation.
Trust me, learning about this wire will save you a lot of grief. I wont try explaining it all to you here for the sake of time. Set aside about an hour for reading previous treads and pouring over your wiring diagram.
I will tell you the exact location of this elusive pink wire on your particular car is as follows. Starting at the ignition switch the pink wire (which looks faded to a brown on my car) crimped and sodded to a female disconnect along with the green-red wire (break light indicator and alternator regulator). From the switched power the wire extends over the steering column under the dash to diver side kick panel TO a bulk bullet disconnect TO a confusing three foot loop back to a parallel bulk bullet disconnect, where it joins a brown wire from starter relay. From there it changes color to red-green, passes through the firewall and joins a bulk bullet disconnect. Here it changes color again to black as described above.
Hope this helps.