My 1974 Ford 3000 has a Zenith on it. 13914. Started leaking gas. Noticed it has a crack in it. The tag on the carb says 13914A and has some other numbers. I've found a replacement that is 13914B. Does anyone know what the A and B mean. Is there a difference. Website says that this Carb 13914B fits Ford 3000 1974. I can't find one with the A. Prices range from $600 to $220. Some just call it the 13914. All of them look just like mime from the picture. Any help would be appreciated.