Kirban has a set for $46.96 and they also have a GNX set,lug nut and lug nut caps, valve stem kit fot $69.95, Then Mark sell's the center cap decals for whatever you want ,they have ones with the T look good on the T's.
JCWhitney sells replacement GTA center caps for very cheap $20 a set. Look up 89 Firebird center cap. These are where Kirbans get theres I believe because I have seen the two side to side and they are identical. GBodyParts sells stickers!
Looks like the metal tabs are the best as the plastic tabs break easy, EBay has a few sets on there I just bought a set,then just get the decals .Not sure if you found any thought this might help.