Thanks Ross.
With the flywheel off, I had access to the plug, or where the plug should have been. I also went to my spare 407 engine, removed the flywheel and looked at the cam plug there. Looked like the same set up.
I bought a new 2 inch convex expansion plug for 75 cents and installed it with the right amount of Permatex #2 (we all know how much that is!). I think it will work OK. I will put the flywheel, clutch, trans, etc back in tomorrow and give it a road test.

Where Are You From? Ellensburg, WA

Do You own a car built by Durant? Yes, several