Coil voltage high engine running

I have points and the resistance wire in place and a 10si alternator. The resistance wire is red, though, and is marked "resistance do not cut", it's terminated properly at the bulkhead connector and looks factory. I read just over 6 volts at the coil with ignition on, but with the engine running read 12 volts at the coil, 14.5 volts at the battery. Weird.
From what I've read should be 9 or 10 volts at the coil?

Its a 1971 GMC 2500, 350