I presume this is for a R34, yes you can put the GT-R bumper and bonnet on a GT-T but you will also need the GT-R front guards as they are wider than the the standard GT-T one's which means you will pretty much need the rear quarter panel guards as well since it will look weird with pumped guards up front and the skinny GT-T rear, and yes the bonnet latch needs to be changed and the hinge's too if I recall.
There's old post's that go into more detail floating round on here if you have a search.