While having the correct number carb. would be nice,don't pass up a good deal on any of them as long as it is for a model B. If you plan on ever running all-fuel stick with on of those models but if gas only or a compression increase is in the works for the rebuild then a gas carb. should be fine as long as it has the smaller throat size of the model B's
A larger throat A carb. will run but really tend to foul out spark plugs.