And let's think a little deeper. Is there a gasket between the block and main cap? No....and the oil is going to leak from the biggest leak first, like your .0025 rod bearing clearance, not where the pump is tightened down. Now, if the surface of the cap is compromised, then the gasket "might" help, but I normally lightly surface the cap anyway. Really it's not gonna make much difference one way or the other, but I do recall tearing down a engine years ago that had that thin gasket, and it was torn and pushed out at one spot. Just things to think about.