I don`t know of one ever being made specifically for the A series, i actually don`t believe there were any ... i made my own single carb one out of late model English 1&3/4 Metro manifolds, it`s not really that hard to do & works a treat

If you nwanted a better one then maybe see Graham Russle but he will probably ask you "Why Bother"
If you havn`t got a 1500cc (or bigger) "Road" engine then i really don`t see the point either.
I have a set of twin 2" SU carbs set up on a late Mk2 "S" type manifold as well
Edit--> & i just bought another pair (Hif type 2" SUs tho) from SpraycanSam