I'm looking at buying a twin carb inlet manifold being offered at the moment. It includes the SU carbs and exhaust shield plate etc. I already have a matching exhaust manifold and air filters. I want to make sure that I am getting the right part for my car. According to my CVI catalogue the manifold should be part number 418910B. The item I'm looking at buying has 418404 cast onto the top of the cross tube on the manifold. Am I looking at the correct twin carb manifold for a B18 engine? (I can almost hear those of you with twin carb B18's scurrying out to the car to have a look!). I have a 1963 221 with the Zenith carb.

What else is involved with changing a single Zenith fed B18 to twin carbs? Is it a worthwhile thing to do without going to a sportier cam and other mods at the same time?