First of all, don't be mislead by the "fail safe". 66 may have well been the first year for Stopmasters. They were appealing because they were compact and therefor fit a Chev and they were lightweight which appealed to bulk carriers. They were only popular with carriers who looked at numbers and not at practicality. Consolidated Freightways was the last carrier that I know of that used them and they were auctioned off in 2001. Parts are very expensive and not readily available any more, and very few techs know how to trouble shoot them. However, the only to retrofit them to cam brakes would probably get different axle housings with cam brakes on them. The plunger gets rusty and sometimes functions, and sometimes not. I have 9 former CF trailers, and I have replaced the axles on all of them. One lot of 4 that I bought in Los Angeles and trip leased them to San Antonio, all 4 arrived with no service brakes at all. However the spring brakes were working. However on a truck as old as yours, there is a very good chance that the springs have rusted and broken The swinging pedal was just not a very good idea to begin with. This is what is standard of the industry now and basicly has been for the 44 years I have owned trucks.
http://www.bendixvrc.com/itemDisplay.asp?documentID=2590. If I were to drive a truck any distance at all I would totally redo the brakes using modern components. However, it is simple for me to do because I am a licensed salvage dealer as well as operate trucks and I always have donors sitting around. As for not having a trolley valve, they are not manditory. Schneider National specs their trucks without them to keep drivers from using them as a parking brake. I personally prefer to have them. We have two trucks that came from Schneider, and we added a trolley valve from a donor.
