Sorry, you must've missread my post above yours.
"After fitting some BBS wheels, there wasn't a full nut's worth of thread sticking out on my GTS-X,so had to go to longer units..."
IE I needed 3" studs after putting the wheels on as there wasn't enough thread sticking through the new wheels. I'd say my stock HR31 GTS-X studs would be the same length as R31 GTS units,and as I said,they were not long enough. Probably didn't need 3"ones,but meh...