Vehicle wants to start when releasing the key

The other day my truck went from firing up every time immediately to now turning over and over before sometimes firing up when releasing the key. It'll turn over without even a hint of wanting to start but as soon as you release the key it either fires up or at least tries to.

I got out a volt meter and measured the voltage at the + side of the coil. It has about 8.5v when turning over and when the key is released I can see a real quick 11v on the volt meter before going back down to 6v with the key in "run" without the engine running. I traced the wire back to the bulkhead on the firewall and I'm getting the same voltage readings there. I also went under the dash and checked the voltage going into the ignition switch connector on the ignition switch side and the voltage readings are all the same there as well. I'm not exactly sure what to expect but shouldn't the voltage be at 12v when cranking and not 8.5v? Before I start blaming it on the ignition switch, I'd like to know what you guys think. This is on a 75 D100 with a 318. Thanks!