I love JBWeld,,, but from the description I thought Mike was wanting to seal to keep the oil from leaking from that hole... JBWeld might leave one with a mess to deal with when a real fix is attempted... or when the pan needed to come off for a regular gasket... If the pan can come off for the fix then someone should be able to heliarc it....or but it really has to be clean,,, then heated and brushed a couple of times... and oil in the pores can cause a bad weld....

Mike ,,, I thought you were going to take a picture of the problem... ? that would help in trying to advise on good solutions...

PS, they have silicones which can be used to make flexible molds in which to cast Bronze.... and the high temp RTV will certainly withstand any temps the block or pan will ever reach....