This is a Delco Remy starter with the foot actuated switch, correct ?
Did you try removing the switch from the starter? When I rebuilt mine, I noticed that the switch has those two small pieces of plastic of each side to keep the main contact from hitting the sheet metal housing (Z in the diagram).
At the time, it just did not seem like the most robust design to me, but I guess it works. If one of them were to break or wear thru, it looks like that contact could touch the housing. That might account for a short circuit which is immediately present when the cable is connected.
