I take it that you have a manifold from a 128 coupe (two barrel weber carb std) this is the manifold to go for (I have the part number thats cast into it around somewhere) This is better than a manifold from say a 128 3p (as here in australia anyway) these have much smaller ports.
The same base pattern is used by all DMTR type carbs (what a 128 coupe has)
the carb from a 128 coupe is a 32dmtr and has 22/22 venturis.
From a lancia beta 2000 you can get a 34dmtr carb, which has 25/26 venturis
from a regata 100s you can get a 32/34dmtr, with 24/25 venturis
the difference may not sound like much, but work out the cross sectional area available with the larger venturis, and its a fair %age increase
If you modify the coupe manifold slightly, you can also fit a DCNF type carb, these have the two throttle blades opening together (simultaneous) as opposed to the progressive type DMTR carbs
Attached is a pic of a 36dcnf carb with a modified 128 manifold, this is for sale, email me if your interested.
SteveC
