Putting booster on 66 drum brakes driving me crazy

[old cool]

I don't want to be redundant 55, but I think you should begin looking at simple vacuum parts before spending on pumps. As I indicated above, your brakes are functioning exactly as mine did when the check valve was plugged off. A check valve is cheap. I would make sure that is doing its job. Best wishes.
Fyi, my booster is the least expense of the Cardones. it is rather slim so i assume it is a single diaphram. It is black vs cadium and it averages about 100 bucks.