Hey Tews,
I'm not sure about fitment on the GSXR front to the CB550. Also are you running the GSXR wheel or the CB550 hub (like the Rusty Olive set up)?
My next project is mocked up with a CB750K2 frame and '07 CBR600RR front. It uses both upper and lower triple trees from the CBR600RR, but the steering stem from the CB750 - along with necessary spacers to make it work. The stock front wheel hub accepts the CBR bearings and I have Brembo snowflake rotors mounted to the hub. The only concern I have is clearance of the spokes (wheels are not yet laced) to the brake calipers. It may require me to mill part of the inside edges of the calipers to clear the spokes. Alternatively, I am wondering if I can run the same set up with tubeless rims (Morris, Lester etc) but I want to find a set with either 18" front and rear or 17" front and rear; that's a challenge!