[Short 3/4]

Can’t be of any help with the wiring of that 76, but as far as your last question, I did the same thing on my 65. I really like a good accurate mechanical gauge, but also appreciate that an idiot light immediately grabs your attention. In my case I put the idiot light in the hole in the head, and the gauge feed to the stat housing. Probably could be reversed, but that worked out best in my case.

Also did the same for the oil gauge/light. Was easy, just screwed a small plumbing T into the block, then attached the feeds to it.

Both have been working great now for several years,

Tom