How do I get the float unstuck in the carberator of a 1976 Ford F100 truck?

If its that old. I would get a rebuild kit and completly rebuild it. Clean all parts real good put new needle valves and gaskets. And possibly float, because more that likely it could have a hole in it and sinking in the fuel. Or the needle valve leaking. The kit comes with a diagram in it of where every part goes. If it dont have one tell em give you one.

An easy way is to remove the air cleaner off the carb, and give the top of the carb a couple sharp taps with a small hammer or a heavy screwdriver.. sometimes you can simply loosen the needle valve and float up this way.
You may need to take the top of the carb off. The float and needle valve work together to stop the flow of fuel into the carb. You want to check to see if the float is not full of fuel.. if it is , then it's got a leak and should be replaced... spray the needle valve and seat with carb cleaner spray to remove any build up.. And as long as the carb bowl is exposed, clean the basin out as well.