OK, just bolting the ammeter wires together doesn't "get" it. You are still faced with the problem of voltage drop/ poor connections in the bulkhead connector
Yup^^^ and just for fun see if you have a ground strap from the block to the chassis. I fixed 90% of my charging issues bypassing the ammeter under the hood along with some new connectors to the alternator and then noticed I had no ground strap. Picked one up at NAPA for next to nothing and really cleared up the rest.