There are the B series three main engines (MGA, Magnettes, Nash Metropolitans, even Leyland 1600 tractors), and the B series five main engines (MGB, Morris Marinas, Sherpa Vans and a jillion other vehicles/). The gaskets are not the same and cannot easily be substituted one for the other. Every shop has one (or more) three main gasket hanging from a hook somewhere.
Use Ultrablack or The Right Stuff between the sump and the gasket; use grease between the gasket and the engine.
Hope this helps.
SAFETY FAST!
John H Twist
University Motors Online
Cell 616 307 6737
www.universitymotorsltd.com