That's really interesting Frank, because that's a key difference between the standard sump on the Morgan and the sumps I have from the Mondeo, which have no slot. This is not a problem since I can use paper, or 'toothpaste' tubed gasket compound if necessary.
Now I have one more favour to ask.
We already know that the Series1 Roadster engine was specced from a Jaguar base unit. I wonder if the 'full waffle' design is a Jag spec sump? So next time you visit the Jag dealer, I wonder if you know anybody there well enough to find out?