The only thing that I can think to look at to see if they are T/A wheels is if they have rear or front written on the back of the wheel. I'm guessing GNX wheels don't say anything. I'm certian there are a few differences though. i just don't know them.
KID
the rims in pictures are rikens , they are a two piece rim (center and outer drum are welded together) and were built by same maker that made the GTA (JWC) available in several sizes , heights , bolt patterns and offsets but if they were on a gn they should be 16x 8 5x4.75 with a 0 offset (4.25"back space) which gives a slightly deeper dish look than front GTAs and fit great on a GN but a little too far out on the front compared to running a gta rear with spacer so you have to watch for rubbing the outer edge of tire on fender in the dips and inner wheelhouse on tight turns
they use cone lugs like the gta but the lugs set in almost completely flush to the face
they use a different center cap (same one as the old kirban enkies) the caps on those are smaller than GTA caps and have with notched edged , the GTA gnx rim used the firebird 3" hex caps
if you look youll see the spokes dont meet at the outer edge where they meet the drum . Gnx gta the spokes come together and are smooth on early GTA/GNX rims , later gtas had a dimple on the spoke ends . the outer drum edge on the rikn has a longer lip than the gta