If your valve looks like this
...pic... it threads to the bottom of the tank.
pipe threads
if it leaks at the stem it can be repaired by adding packing under the gland nut.
Just cut a small piece of graphite rope packing. Add it and tighten down the nut.
In my 50 the fuel line goes to a flex hose. Flex hose to valve to allow for movement of the cab.
