I made a mechanism for my GMC from a vacuum advance,as per an article I saw on here someplace;it wasn't hard to do,and it shifts the speedometer just fine. I can't find a speedometer cable that works for mine;it's square drive at the speedometer,but old style round with a blade on the end that goes to the Brownie (Military?),unless someone makes an adapter for one end or the other. (I've seen adapters on eBay,but not being able to pick 'em up and look into the ends,I can't tell exactly what they do.) I asked the mechanic at a Truck Shop about it and he just stared at me like I was crazy.
Speed
