Dave, the standard 5 screw sender flange has a rubber gasket. This gasket is very adequate. It's only splash "pressure". It won't leak. The screws won't leak.
If I had a AD, I would use/modify a TF sender/pickup. They draw from the top. So do 60-66. Plug the tank at bottom with pipe plugs, no valve. The 59 motor you have in the 50 has a fuel pump designed to draw from a top outlet sender. So no worries there. These say they work with your tank. 49-53 and 54-59 ??? check it out
Have not read on here that anyone has used this on 49-53. But the web says it works. This style avoids leaks in cab.


Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn