Not a stupid question at all mate.
I believe it depends on which head you have on the A12. If it is one of the round port varieties than the manifold won't be any good for you

. I do have the carby adaptor plate that you could use on your manifold though.
The carby will most likely have to be tuned to suit your setup, but yes it would run your car tuned right.
Hope this helps mate.
Clay