I remember dealing with that many years ago.
It’s really a bandaid situation in that it’s much better to do an oil pan gasket as a single unit AFTER the timing cover is in place......but that’s not in the cards at this point.

Cleanliness of the oil pan area is really important....degrease the corners really well. Install the cork piece with a little rtv where it meets the old gasket. Install the forward oil pan bolts first and tighten them down——this will pull the timing cover down to the oil pan so the bolt holes line up. Then attach the timing cover bolts.

If I was doing a BB timing cover onlyagain I think I would ditch the cork piece and use just rtv.