The SD40 and the SD45 chassis are similar, and the shells may be interchangeable. The SD70MAC shells are probably interchangeable. The SD80MAC and SD90MAC shells are probably interchangeable. And that is it. The SD40 and SD40-2 are not.
I took an SD40 snoot nose (Kato), and chopped off just enough of the short hood snoot to make it an SD40 regular short hood. It worked just fine. The deck under the upper shell apparently is designed for both shell types (SD40 snoot and SD40).