ABS was standard before 1990 but an "improved" system was installed in 1990 supposedly improved yaw control. Early electronic stability control before "Stabili-Trak" in 1995.
LPTWS is standard too.
I've read that the "build sheet" is glued to the top of the fuel tank. Not sure of the survival rate of a sheet of paper on the tank. LOL
Leather seats became standard around this time too. (I think).
Z51/FX3 was optional except on the ZR1 which it was standard. I too have the two top option. I think my coupe has every possible option except the Delco-Bose Gold but I have the six speaker set up. The sheet in my console is full of RPO codes.
I also have the 3.07:1 diff which may have been required with the Z51 but it is listed separately.
When I added up all the prices for the RPO codes plus base price mine was well over $41,000 new. I can't imagine spending that on a car in 1990. ZR1 were an additional 29,000 bucks. OMG!
I think something is incorrect with your car with regard to the interior. Either the RPO list is incorrect or it has some hybrid option on the interior especially considering the dash, steering wheel and console being black and the rest tan. Very strange.
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If it isn't broke, I haven't fixed it yet....