There is a relocation kit for the Busa, that mounts the rectifier on the throttle side of the sub frame, about mid way.
On the outside of the subframe.
So it's not visible with the tail on.
I think Blancabusaless had pics or video for the Busa tail.
The gsxr location should be the same.
I've never put a 1k tail on a Busa, but have had the tail off several gens of the 1k, and there is room.
Sorry, all I got.