You are missing a spring, the scoring looks to be from some object/debris that got lodged under the plate. Don't see a problem with the parts washer approach, all parts are metal. As dirty as the item is, the shaft/bushing is probably worn. Extremely hard to find the small pieces to replace. May want to place ad in "parts wanted" or check your local parts houses...they may know a reliable rebuilder in your area.


http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm1225.htm


Ed