if you download the routing templates from those links I gave you, that should be the easiest way to tell if it'll fit or not- you'll probably need to take out your current trem to measure your guitar.
you can use your current studs, but they won't be as high quality as the gotoh ones, and will also void the warranty on the gotoh trem (i asked them the same question!).
i think it tells you which nut th r2 and r4 are on the floyd rose website- if memory serves the r4 is 1 11/16" (43mm) which, being an ibanez, is most likely the one you want. Bear in mind, though, that the Floyd Rose studs are quite big too, and still may not fit.