I have a 87 MC SS 305HO. So I developed a coolant leak at the rear coolant cross over at the gasket on the intake. I removed the intake and saw that the gaskets have block offs on both rear sides of the head with a small hole in the middle. Im assuming these are original due to the engine only having 89,000 original miles. Do I have to put the exact same gaskets back on or can I use open ended port intake gaskets? I have a new set already from a auto parts store auction I went to a couple months ago. And whats the deal with the blocked off ports anyway? I've only seen block offs on the exhaust crossover.