Factory ammeter
I used a small grommet in the firewall but was considering a factory style one if I could have found one. They look like a big bottle stopper. If I had also run the battery wire through the firewall I would have kept looking for a bigger grommet.
Your '75 firewall may be a little different, but the indentations for various unused optional pass throughs will be there.
Here I'm starting to mockup the length of the wire from the alternator.
It goes to the ammeter's black terminal. I had the instrument panel out anyway for speedometer repair so this was a good time to do it. The ammeter connections in the rally panel are difficult to access with the panel installed so I had been waiting for the opportunity.
I used a small grommet in the firewall but was considering a factory style one if I could have found one. They look like a big bottle stopper. If I had also run the battery wire through the firewall I would have kept looking for a bigger grommet.
Your '75 firewall may be a little different, but the indentations for various unused optional pass throughs will be there.
Here I'm starting to mockup the length of the wire from the alternator.