Before installing the plate to the engine, lay it on a flat surface and insure that the center hole is raised at least 1/16” up from the surface. This will insure that the plate will tighten up enough against the outer gasket to prevent leaks at that particular gasket. If there is insufficient clearance, then here’s a link to the reposted Walt Nuckels page that explains how to quickly fix those plates that are deformed enough that they will not tighten sufficiently.
http://www.y-blocksforever.com/tech/html/oil_filter.html