At least you have that problem nailed. Now, about those wires at the gray connector...

If memory serves, there are only four, even though the connector has pigeon holes for eight. Yellow, red, black and blue.

Red ends up at the alternator, after going through the under-the-engine-front harness. Black ends up at the oil pressure sensor, same route as red.

Yellow connects to a sender on the block, I think it's the one for the temp gauge. The blue, as you know, is the starter starter. Make a sketch of which one is in which pigeon hole.

Unlike the other wires in the main wiring harness, those four can be by-passed. By that I mean to put new wires in at the gray connector, connect to the destination lugs and leave the old wire remains in place.

For the gray connector, use the existing terminals soldered on to the new wires, unless you can find new terminals of the correct type, I couldn't. You might even find (AutoZone, NAPA, etc.) wire of the correct colors.

The red and black can be run across the firewall and down the RH fender. Leave a lot of slack since the engine will move when in use.

The blue and yellow will need to be "finagled" (engineering term) under the intake manifold and thence to their correct destinations.

There are other wires inside that main wiring harness that might be useable unless the harness is moved about. If they go bad, the job is a magnitude larger than the four simple ones.

Good Luck,

Bob

:>)