UPDATE!......
Alright so I've covered up the gap in the above pics with some felt tape which I think will do for now. It looks ok in my opinion but...
I also hooked up the electrical aspect of the gauge/live unit. And just for future reference, I used the 12v front/rear outlet fuse for the switched power and the telephone fuse for the constant 12v power. I then tapped into a ground wire near the hood release, it was pretty easy.
That dang firewall gave me some issues though I didn't have a good wire fishing tool to route the vaccume tube, so I'll have to complete it this weekend. I'll probably post final pics then. Again just an FYI.