Gus is currently making a manifold to use the same carbs as you on a 2 ltr black top zetec. I have also done a similar setup on a cvh using the original bike carb rubber mountings, and without respacing the carbs.
Basically we have got a plate to suit the head, and a plate to suit the carbs. Pipes then run between the two plates with them welded & internally ground as needed to match the ports.
Hope the above helps