Manifold heat control valve replacement?

Just brought home my new daily driver. 1964 Dart 170 4 door. Its equipped with the 170 /6 and push button auto trans. I pulled the intake and exhaust manifolds to fix an a exhaust leak. I noticed the rotating wheel and spring are not on the exhaust manifold. After I have the manifolds off and separated, I notice the heat control valve is completely stuck and wont move. It is in the vertical position, so exhaust gas can move upward and touch the bottom of the intake, or travel down and out the pipe. I want to replace this mechanism but cant locate parts and or instructions. I am under the impression I will need an exhaust manifold? Any thoughts or recommendations will be greatly appreciated.
Doug