Also, there are two styles used on the older GM products. I use gasket dope, such as Permatex #2 or Indian Head Shellac with both.
One is a disk that has a curve to it. Place it in the hole, dented side out, and drive it in until it flattens. That expands the disk to fill the hole.
The other has a flat base with the edge bent straight up.
Put it in so the cup is open to the outside and drive it in. It's a tight fit, but drive it in until it's seated.
