Another Air BrakebQuestion

[greywuuf]

Having issues with the air brakes on my "new" 1974 Chevy H70 (with a 6v53). New to the "heavy" side of things and it is kind of hard finding good info on the "obsolete" stuff. Does anyone know if these older trucks have dual system brakes....with spring relay valves and the attendant hardware? I am trying to learn about it on my own, and it is currently not stored near me ...any run down on what components should be there and how they work.....or a link to a directly pertinent source would be greatly appreciated.