Oil pan seal?

I orderd a complete engine gasket kit from fel-pro for a 77 360 4brl and the rear pan seal is to large. I thought maybe it was mispackaged so I went to the parts store told them year and engine type for a mopar they had a pan kit there got home sized it up and it's still bigger then the one I pulled off. Is there two different sizes? It is a 77 360 with center sump stock pan its no other small block can read casting #'s perfectly.