The timing is on the "ball".
Do you have a timing light with an advance function? I went through this very issue with mine. Did some of the same things you have trying to chase down a "fuel problem", until I happened to have a chance to talk to my uncle, who had a virtually identical setup in a '49 Chevy Business Sedan back in a mid-'50s. I told him what it was doing, he told me to advance the timing about 5 to 10 degrees. Sure enough, that fixed the problem. Haven't had an issue with it since.
