The WT & WA only stand for different "style" and the #'s do to a point. For example: A WA167, WA142 & a WT433 are the exact same size carb. The difference being the WA167 has a choke & primer bulb, the WA142 has no choke or primer bulb (my favorite for engines not coweled in) and the WT433 has a choke but no primer bulb. There are also small differences in little thingy that you hook your throttle to. There all in the same place but just look a little different. I'm sure there are many more Carb model #'s that will end up being the exact same size. I wouldnt worry about the WA or WT thing, I have all 3 of the carbs I have listed & one takes no preference over the other.