Take a look at your side marker lights and tail lights.
You can get weird readings with burned out filaments.

Alan wrote:

The right measures 12.7 at the bulb, but the left only measures 10.5. Any suggestions as to what is causing this?  Turn signal switch?
 

Could be.  Is there a good ground to both of the lamp sockets in the buckets?  Have you tried swapping the bulbs from one side to the other (it's unlikely that the issue is a bulb but it could be)?

I would check the resistance between the less-bright bucket and ground.  It should be zero ohms.

There are two separate wires that come from the turn signal connector to the rear turn/brake lamps.  You could disconnect and reconnect that connector a few times to clean the contacts and confirm that none of the contacts are pushed out of the connector.  My wiring diagram says that there is a connector between the rear lamps and the turn signal connector.  You could try disconnecting and reseating that too.  It should have an orange/blue stripe wire and a green/orange stripe wire.

I am measuring the voltage on the wire coming back to the rear and using a good ground on the meter so i don't  think the ground at the bulb is the problem. Will do some more looking this pm.
 

Power comes from the light switch (there is a circuit breaker in there and the lights do no have to be on). Then it goes to the brake switch (you are good up to this point), and from there to the turn signal switch where it goes to each side. This is done to interrupt the power from the brake switch when the turn signals are on, or you wouldn't see it blink with the brakes on. The turn switch could be partially fried (high resistance) or a bad connection/wire somewhere. If you have a wire diagram, see if there are any plugs on that wire. I believe the brake/turn signal circuit is the most often asked about circuit on our cars.

There is a green/orange wire on the plug coming out of the steering column. This goes to the left turn/brake. If the voltage is good there, may be a bad plug connection. If it is bad there, may be in the turn switch. Orange/blue is the other turn/brake.