I thought I found the answer….but no

See in the picture the one 12 inch black wire. That is all you need. It goes to a Battery bulk head in the first picture. Then I added a normally closed relay to shut the alternator off when on the start line. I use to have a short wire going to the bulk head for the battery cable. Then I put the relay in line seen in the second picture second picture

View attachment 1716075007

View attachment 1716075008
Thank you