Well, it's hard to tell you where the text is because I believe nobody ever looked into translate any GT.
Anyway, the text can be compressed or use a custom table or even be graphics (like you saw with the car names).
Just by a quick look at the structure, I can say that what you are looking for is:
-Faulty.psx: all 00 so only padding file
-GT2.ovl: possible compressed data
-GT2.vol: probably the most data is here
-music.dat: probably only the musics of the game
-SCES_023.80: the executable but because so small, probably it's really only the main program and no data in there.
-stream.dat: the movie of the game
-system.cfg: system file
At the beginning of GT2.vol there are 3608 tims but only the cars names and the wheels.
Anyway start from here
and choose your level of knowledge. You should find all the advice you need there.