Thank you very much for your answer.
Yesterday I gave it another try.... I readjusted the carb again according to the shop manual - BUT I set the floats higher and used a bigger jet). I noticed that the engine runs very smooth but the warmer it gets it starts to run very rich (much black smoke)! And in the end the RPM drops and the engine dies. I did the carb adjustments on a warm engine (10 minutes running on idle speed). The actual problem starts about 10 minutes later. Afterwards I decided to do a longer testdrive.... it's getting worse. I conclude my engine gets a way to rich mixture (the black/brown spark plugs seem to suppport my guess).
I also called a friend who owns a ford garage. He normally takes care of my Mustang but he's on holiday right now: He suspects a faulty motorblock gasket somewhere (intake manifold?). Would this explain the coherence with the temperature?
During the next days I'll do the tests and modifications you suggested in your last post.
I'm also thinking about testing my Mustang with my other (old) Autolite 4100.
I'll keep you updated.
P.S. If some Pony Carb guy would read my post: thank you for NOT answering my emails!
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