>racer would put on a 2 inch SU off a Jaguar or something, My oft faulty memory says there were three basic SUs - the HD-4, 1 1/2" throat used on MGA, the HD-6, 1 3/4" throat, AH 3000, and the HD-8, 2" throat, Jag E-type. They were good carbs when new but do not know how they have aged. Believe there were also some Japanese knockoffs also. Padgett