Mate, i tried to use the GTS-t bonnet and trust me when i say it doesn't fit. As for all the other parts such as the headlights spacers, which moves the headlights foward an inch as the bonnet is longer, side skirts need to be modified as the guards are flared, indicators obviously have to be changed, gtst front bar wont fit without mods either, guard raisers as the guards sit higher, hence why u need different or modified hinges.
I've done this along with a few others here in Melb, and they will confirm with me that these parts/mods are necessary. You wouldn't really know until you do it, as that was the case with me.
And yes my brother has a GTR R33 parked next to my car in the garage and they do look very similar in dimensions etc, but thats wasn't the case.
I'm not saying your wrong, but in my quest to do the conversion those where the obstacles i had to overcome and using GTR parts was the only choice i had other than modifying my parts.