777 is tied to an address in Dearborn, not a particular product. When you hear a 777 project, that can mean either a Roush project or a Roush/SVT project. There have been many.
777 Republic Dr., which is not coincidentally next door to SVT.
777 is most commonly used in reference to the engine in Don Bowles Roush Mustang. It might be used for other things but for most it's in reference to that engine.
Not being a dick but Republic Drive is in Allen Park and saying there's a Roush building in Allen Park is like saying there's a stop sign in Allen Park. There are a lot of them. lol