On Mark IV BBC there are 2 irregularly shaped coolant holes at the rear of the block on each deck, a large one and one about half that size. However every gasket I've been getting the last few years (fel pro) only have an opening for the smaller one. Looking at my old engine building books they show the gaskets with both holes. Why did they do away with gaskets with both holes or do they still make them? If so what is the difference of running the engine using both hole or not?........ just curious