I found the cause and a little bit of nightmare-fuel. The main issue is that the fuel sender assembly was not seated into the tank and the bung nut was not really screwed on.

Also, it's a Regina car with a single pump... uh it *was*. Only it isn't anymore. My late friend did some weird stuff. I think he plumbed in a Bosch pump I gave him, but the fuel lines and wiring are all kinds of sketchy. It looks like low-pressure carburetor fuel line even after the high-pressure pump. SOooo... that will be an afternoon or more to fix. I'll make a post about that separately, probably.