If I am understanding the question correctly, the "extra" hole in the flexplate is for the alignment dowel in the end of the crank. The shield should be the same for any PG with the same size flexplate. You can one from a junk yard, any racer who runs a PG as most do not use them or probably even get a chrome one at most speed shops.
As far as the flexplate itself is concerned, check it carefully for cracks. If there are any replace it. Make sure where it mounts to the crank and the crank itself are perfectly clean and smooth. Also check the teeth to make sure they are good. New non-sfi plates are cheap, so if there is any doubt......
