Forget the Magnum block. Just make sure the gasket matches the head. Cometic has a number suggested for stock cast iron LA heads, and a different one for Edelbrock Aluminum heads (and all copies like Promaxx and Speedmaster). I think there was another number for Magnum specific heads, but the block is basically the same as an LA.
Pretty sure some of us are running whatever was in stock and they still work.
