UPDATE
So I put off swapping in the engine and went on another search for a manifold and here's what I found.

H95 oval port intake manifold.

So I'll end up using my A12 carb on this or see if I can find a second hand 32/36 Weber in good condition.
I just have one more question, will my A12 exhaust bolt back up to the A15 head and manifold?