Can any one shed some light on reparing the brakes on a 73 chevy C-60. the system is a single line master cyl. that runs to a vacuum boost chamber under the driver side of the cab. then out to the wheels. I have replaced the master cyl. wheel cyl. and all lines including the vacuum line from the eng. to the vacuum boost chamber.the pedal is hard but no brakes. I fear that the only thing left is the vacuum chamber. if this is the source of my trouble can I rebuild it or must it be replaced. or I'm I missing some thing simple.