Hottroddd57,
If you are worried, you could invest in three senders and put one in each head plus one in the intake manifold. This would allow you to run a test to see what the offset is between each location. It really doesnt matter where the sender is located after you have a baseline....you want to look for changes from normal....whatever normal is. For instance, if your gauge reads 205 deg in normal summer traffic and one day, it goes to 235, you are alerted to something changing for the wrong......that's why a lot of gauges dont have numbers....so people dont get caught up with the number and they will react to the change.

A common error in gauge mounting is to use a pipe adapter that shrouds the sensor probe end. For engines that mount the sensor vertical, the pipe adapter (bushing) can trap air around the sensor tip and theoretically affect the reading by insulating the tip. I usually try to find a bushing that allows the tip to be extended a tad.
that's my story and I'm sticking to it.
mike in tucson