New positive cable and beginning of trying to figure out where the second battery used to connect. Current theory is this battery actually should go the left side of the solenoid and the other battery should go where this one is right now.
View of the leaking radiator cap and battery isolator wiring. Leaking cap turned out to be a dent in the filler which was easily fixed.
Another view of the nice new cable I payed NAPA way too much to make. Price would have been fair if their workmanship had actually been better than my own. Apparently they also are in the habit of forgetting to put the shrink wrap on BEFORE the connectors.
Motor after a little bit of work with some simple green and a few rags. Turns out the "leaking valve cover" is just due to some old hardened grommets, nice $2 and elbow grease fix.
Original battery cable on the left, new replacement on the right.