We have done a couple of the 65/66 Chev pickups where we put the volt meter in the circle the factory used for a tachometer. To balance the instrument cluster both a volt meter and tach are installed. Do a search for Chevy truck with factory tach to get a visual. I am a fan of idiot lights IN ADDITION to gauges since they are akin to hitting a spaced out driver between the eyes with a good sized mallet.
