here is a definite answer then..
a 01-03 gsxr 600 swingarm,unmodified,will not run at stock height on a busa..
it will run,with threaded lowering links,and a 600 pivot,close to 1.75 lower...that is the HIGHEST you will be able to run it...
with 3 hole links,you can only use 3rd hole(lowest setting),as 1st hole will hit,as will second(VERY SLIGHTLY),hence using threaded links you can fine tune it closer then 3 hole links..
using the 600 pivot is a MUST,as if you use the busa one,the bike will be unrideably low..
hope this clears things up..mike