If you scroll down on this thread it shows a common air valve that was used on a 2 speed apparently as original equipment. http://oldgmctrucks.infopop.cc/eve/forums/a/tpc/f/993000056/m/694101484 I think this is the route I will go instead of trying to fix the complicated valve on the firewall. This is a common valve that is still available. The one pictured has a plate that is identical to air valves. The screws go through the plate and screw into the valve.