From what I can see on my car, wing is straight bolt up once holes are done. Front bar should fit with no problems I reckon. Depends on the flaring for the guard mount point, same goes with rear as the GTR guards are flared a fair bit more than gtst’s.
Only part that I can see that need some cut and welding is the bonnet latch for the GTR bonnet. It appears about 2 – 2.5” shorted than the GTST one (compared my one to a mates gtst bonnet latch.
Only way to be really sure about front rear and skirts is to find someone with a GTR and do a test fit :-P