I suppose you mean the rubber seal its to keep the air deflected into the radiator and not bypass into the engine.
Not the deflector that sits directly in front of the two forward carbs but the one that is at the bottom rear of the radiator. The manual I'm using calls it a "rubber seat". It's probably 2" X 8" and hooks onto the two lower brakets that hold the fan. Is that the one you're talking about?
It's on a '99 Standard.