In concept, I wanted the voltmeter to do more.  Power to the fuel pump is a critical gotcha moment.  It could be the pump or the fuse or a short if you have issues.  The 75;-76" cars had front mounted fuel pump and a heavier wire, so I was less concerned.  But it made sense to get the positive from the front trunk fuel-pump wire and run that thorough the harness when I re-wrapped it.  What you see in this image is the area under the gas tank being setup with sheathing and the extra wire that goes to the voltmeter.  I even soldered it.

Note the shrink-wrap that has not yet covered this + lead.

Here is it routed into the original connector for the fuel pump.  Yes, I am using the older-style 3-port fuel pump from the 74'

The positive is the thicker left of the indent.  The typical Porsche brown ground is to the right of the indent.