No, the GSXR spline is different.
Some where though someone mentioned what was the same spline as the kz650 but I can't recall off hand.
I'll have a look...
...04 YZF600R shifter shaft has the same splines as our kz650's.
...the r1 splines are a fit also, iuse rear sets off a 07 r1 on my 650 the only problem i had was that the shift rod was on top of the shifter and it wont clear the engine so i used a zrx shifter pedal that has the mounting point below the shifter, and no it wasnt a simple exchange had to make a bushingto get it too work.