Do as Soundguy says, crack carb bowl drain, if no fuel, crack fuel tank cap, listen for pressuer sound, that could be vaporlock.Also ck sediment bowl an d screen and strainer in fuel tank tap for being plugged. If problem is no spark, could be coil or condensor gone bad. Will tractor readily restart or does it need to set. Does problem occur more in hot weather,under heavy load and low tank fuel level,these conditions favor vaporlock/fuel "boiling" in Fords of this vintage.Is the guard between the muffler and fuel tank intact,and is fuel line run above this guard? If vapor lock is a persistant problem you mauy need to reroute fuel line and extend it out a little further from the muffler. HTH JK