I understand, I like my truck, but it isn't really a major life priority. I just come here in the mornings before work. The reason I am saying crack, is unless there is something you haven't mentioned, because you forgot, just plain missed, or didn't think it would be applicable. It doesn't really seem like running it for a couple of minutes without water would hurt much, but since on these engines, the head gasket doesn't really separate water/oil any where. (maybe the '61, with the oiling to the rockers) And the fact that if it was going into the cylinders from any source, it wouldn't run out, they ARE pretty well sealed units. And if you haven't taken any plugs or any thing out of anywhere leading to a water jacket/oil residing area. There isn't a whole lot of other options. These relatively complex castings need to be cooled properly or you will get one area expanding at an accelerated rate while the other area isn't... with nothing (I.E. water) to help distribute the heat more or less evenly to the other areas of the engine. So yes I would think you would have to consider a crack. Not to mention it is 50 some years old, and it is pouring into the engine as fast as you can pour it into the radiator.
