I replaced the tranny in my '71 a few 1000 miles ago with a freshly rebuilt one. Is it a good idea to change the tranny oil now that it has some breaking in miles on it? If yes, is one brand of 80-90 weight oil better than another? When I took the distributor cap off on top of the middle of the rotor and on the little metal post that is inside the middle of the cap where black and gritty? What is that about? It was not like this when I switched the electronic ignition on the side of the road a few weeks ago. The Bus seems to be running fine. Julie