Robert - my advice would be to keep the 3 main MGB (which is also what I use in my Mk 2). better engine, more power and it looks right! Bill In a message dated 19/01/2010 6:20:59 A.M. Pacific Standard Time, guinness at stclegal.com writes: I have a 1961 MGA 1600 with a 1963 3 main MGB engine (while the original engine awaits me to rebuild it).