OkWithout knowing much about this car, it is hard to diagnose. Is the alternator output stud wired directly to the battery positive? Is there some sort of ammeter bypass done? KOER, you should have 14v or so at the fuse box.
I did do the ammeter bypass. The two ammeter wires were spliced and soldered in the dash harness. There is a wire direct from the alternator output (with fusable link) to the starter relay. Another wire from the relay passes through the original bulkhead fusable link, and through the bulkhead. The original dash harness (red wire) picks it up from there. The return power wire (black) ends on the interior side of the connector - it does not continue on the engine side.
As expected, the voltage comes up inside with a rise in RPM's.
With the engine running, and the battery charging above 13.5v, check the voltage at the starter relay stud on the firewall, and work your way toward the fuse box. You will find it.