pretty much every thing is different on the itr and gsr valve train.
intake and exhaust cams are different,both valve springs are different, but you could get itr intake valve springs then move your gsr intake valve springs to the exhaust side and install the new itr intake valve springs,intake valve is also different on itr.

if you wana use itr cams but not change the springs you could do that also but remember that gsr valvse springs are weaker than itr so your valves may float sooner, which means you can't take it that high of an rpm. as with itr springs