OK, I believe it was the vacuum advance line I disconnected, not an outgoing fuel line.
That said, I have checked, step by step, from the pump to the carb, to the fuel bowl, and down the throttle body. I pushed the pump piston and gas came out a hole, and the power jet assembly (I think) in the float bowl pushed down and sprang up. When I took off the throttle body there was gas going into the governor throat. So I think I am OK on getting gas to the engine. I sprayed some starter fluid in the carb and cranked her over. I got a couple of gasps and finally a small bang. That's all, but I could smell that something had caught! I can't get any more than this, though. What next?

1953 GMC half-ton