The MGA MK-II car in 1961-1962 had a lighter flywheel nearly identical to the early MGB. MGB uses 3 alignment pins for the clutch cover where the MGA uses 2 alignment pins. Otherwise the 1955-1964 flywheels are physically interchangeable. For street use I like the lighter flywheel (8-1/2 pounds lighter) from the late production MGA 1600-MK-II or the early MGB. I also like the action of the MGB pressure plate, especially with a slightly uprated engine.

The picture here shows the machining required to convert an MGA 1500-1600 specification flywheel to either MGA 1622 or early MGB specification. Dimensions are in inches. Machine out a 1/2 inch deep pocket in the front face as shown, and install the correct number of alignment pins. The flywheel will need to be balanced again after machining (or at least check the balance). Weight is reduced from about 28 pounds to about 20 pounds (plus ring gear).


Also note, from Confidential Service Memorandum MG/267 dated 29 July 1959:

FLYWHEEL DOWELS

To facilitate removal, a 5/32" hole may be drilled from the back of the flywheel into each dowel hole.

This will allow the dowels to be knocked out with a 1/8" punch.