I'm currently in the process of installing an electric pump. I have a new rubber fuel line running from the tank to a clear inline filter in place just prior to the mechanical pump. New rubber line from the filter to the pump. The problem has remained.
Regarding gravity feeding the carb, I don't know of a safe location to mount a temporary tank so that I can drive the car to replicate the problem.
If nothing else, I've gotten good at pushing the car and won't need to get a membership to the gym.
