stock 1973 318 V8 starts but won't idle without foot on pedal

I finally solved the problem! I had the carburetor rebuilt and then I adjusted the mixture screws properly and it idles like it should now. This is the short version of the story. I have been stumped by this all summer. In the end I learned there is no substitute for doing the research and learning how to do it yourself. Professionals do not even have enough help to work on modern cars these days much less put time in on the old ones. Thanks to all who responded!