Did the 74 CJ have a valve or just a pipe? I assume that's the vehicle you're using it on.
Vendors like www.americanpartsdepot.com or www.kennedyamerican should have the valve.
My 69 AMX uses a cable controlled valve that screws into the manifold like the one here for $79. http://www.americanpartsdepot.com/cores.htm
Bob
tufcj