Check the vent. (on newer models, mounted on the top of the extension housing).
Sometimes they get smashed down, and rendered useless.
On high HP, (high rpm), applications, a person usually has to put an extension on the vent, and run a tube up by the rear of the intake.
Did you change both the selctor seal in the case + the o'ring on the k/down shaft?
For the dipstick you could get hold of one from a later model car that has the lockdown lever or hook a spring on to stop it popping out..