it sounds like you are just going to have to do this the old fashioned way. Just figure it out. Just saying "a wire hanging down by the starter" doesn't really mean anything to pretty much anyone. In the period of anywhere of 30-60 years (we have no idea what year your truck is) a lot of things can happen. Previous owners can (and many times do) really strange things, add devices, remove devices, repair, ruin, and/or otherwise disfigure things. A picture might help, with the information given we don't stand a chance. "connects to a part in the block?" Really?