One more thing to check especially if you have recently replaced the gas cap. These trucks require a vented cap or they have similar symptoms. Run a ways and then act like they are running out of gas. After it stops for a while you can start it up or after you open the gas cap to put fuel in it because you believe you ran out of gas.
I went through three new caps that were supposed to be vented on my 51 Mercury before I got one that was actually vented.
A sure sign is if you hear the sides of the tank pop back out when you open the gas cap right after it stalls out.
I would still check the choke and check for a plugged fuel line though. Both are pretty common things on these old rigs.
I would also suggest putting an inline filter between the tank and the fuel pump. That has saved my bacon more than once and it is a lot easier to replace a filter than a fuel pump or carb.
