I would avoid using a factory lly horn at all costs. the s&b horn is pretty low-profile, and there are a few custom ones out there that are a bit thinner even. The factory LLY horn flows like complete garbage.
The LLY mouthpiece will attach to an LMM turbo, but as has already been mentioned, the factory LLY piece is garbage. If you're looking for one that is shorter in length where the intake hose attaches, the S&B is a very nice piece that will work well for you.