There are no lock washers so vibration can loosen the bolts and gravity backs them out.
No room for a nut or anything more than the U nut under the gasket. The offset stamped in the metal is about 1/4 inch at best.
This is true, on top of mine being firmly seated still after 40 years, you could add lock washers. I'm not trying to up sell the idea, it's an option that keeps you from being on your back fiddling with nuts. Somewhere no guy deserves to be.