[51woodie]

My first thought would be a air leak in the manifold/carb area. Check any rubber hoses for loose or cracks, There must be an air leak if you need to have the idle mix screws out to get enough fuel for it to run. One way to check for leaks is, with the engine running, using an unlit propane torch, pass the nozzle around the intake manifold and carb base in close proximity to see if the engine speeds up. An increase of engine speed indicates an air leak. Connect a vacuum gauge, and refer to the attached chart.