It seems like some old car and truck parts are getting harder and harder to find. Going over the 1975 Ford F350 tow truck I purchased recently, we found the brake pressure failure switch on top of the brake proportioning valve leaking a bit of brake fluid. The switch screws in and out and looks like an easy replacement, but just try to find one. I have tried auto parts stores, Ford dealers, Rockauto.com and eBay. No luck. We've been told that we may have to get a new proportioning valve, but so far we have found these available only for 1976 models and newer and it seems like some proportioning valves do not sone with the switch??? On the other hand, we needed a cam for a 1950s Dodge flathead six that we're rebuilding for a customer at Gunner's Great Garage. One call to Northwestern Auto Supply in Grand Rapids, Mich. was all it took to get a new cam for under $200. W hat's wrong here? Why is a 60-year old part easier to get than a 36-year old part?