Carters are probably the best for 1-bbls. They are the most tunable and easily available carb that will fit. Be prepared to tune, there is no direct bolton that works right out of the box.
I have also thought about using the new Solex carburators that JCW and others sell for replacing the carb on Willys Jeep flatheads. They are based on a VW carburator and might have tuner parts available if you look.
