The type of carb really doesn't matter just as long as the carb will fit snuggly into the intake manifold (where the carb meets the engine). I'd get a two needle carb, preferably a Novarossi or O.S. carb because they are the best that I have come accross in holding their tune. By getting a new(two needle) carb, it will greatly affect the engine's performance for the better. The best part is: You don't have to make any other mods to the engine to make it work. Just put the carb in, tune it up, then let'er rip!