Mechanical or electrical fuel pump?
Could rust or other debris be in the tank and be obstructing the lines?
You could remove the gas line to the carb and temporarily route it with some extra line to an empty gas can and see if it pumps anything into it while turning it over. If it does pump gas, then your problem lies in the carb. If it doesn't, the problem lies below the engine.
If it doesn't pump any gas into the can, you can hook a vacuum gauge up to the end of that extra line and see what PSI it is pushing out.
Dave