I don't if it's a w or w/o ac or an issue with years, but I'vd ran into the problem: There is a short snout and long snout. The bolt pattern is the same but one pump is something like 4 inches tall and the other is 4 & 1/4, or it's 3 & 3/4 and 4 inches. (My w/o ac garbage can bulit set-up requires the short style pump.)

Come on guys! Many of you are walking textbooks on these things. Make sure that joes burd doesn't learn the hard way.

Anyway, have the old one with you. Lay it flat on its mating surface; likewise, with the new pump. Check the height of both pumps. It's quite obvious when you look at them, and it's more obvious if you install it and see the problem with belt lineup.