Flyboy,
Duke's designs were 2 needle and 3 needle carbs. A bit trickey to tune, but with the right nitro don't need much adjustment after that. After he died they went to an unusual air bleed type that had a metered midrange. If the midrange was right for the conditions they ran great, if not there was no way to adjust the midrange except to file the midrange port in the barrel. The new carb is similar to the older MKX twin needle which worked fine.