I saw Keith, the mechanic from Northshore Sportscars at a car show and he mentioned having the head sent out for the weber conversion. If you already have the Webers or Dellortos, then that would be the way to go. If you don't already have either of those carbs, it is a lot less expensive to go with the Mikunis, they pretty much bolt right to the inlets on the Stromberg cylinder head. Mine came with K&N air cleaners too.
Another person you could ask about who reworks the head for Webers, is Barry at PHP Racengines in Wauconda, IL.