Brendan,
Any update on this post? I have a '52...similar problem..... Good flow into the pump..very little out.... Carb dry as a bone but will run with a gravity feed...
I was going to ask if the pump could be cleaned or repaired but haven't seen indications of that being likely on this web site.
I'm checking the vacuum and will probably take the pump off next....
I have the original glass cap on mine.....

If the cam is bad on the engine... I wonder if an electric pump is the alternative.
Anyone have a diagram/explanation of the entire gas line system?