i'd do the headgasket for sure!
change for a genuine ford item and i would have thought that you would be fine,
it may have been rebuilt with a new gasket but who's to say that the gasket was fitted correctly/incorrectly?
the back pressure from the engine to make the hoses rock hard would not be from a water pump, and if the gasket is blown across a water jacket to cylinder then you wouldnt always loose water.
its an afternoons work to whip the head off, ford gaskets arent to dear and whilst ur there i would replace the exhaust manifold gasket with a genuine one too, just to be on the safe side as when i remove mine they never reseal properly!