Barry, I can help you zero in on what you need, but I don't know if I can do this today.
No A21 code. That is elastomeric bumpers for '70-'71 cars.
You probably meant A12, which your car is not. This is the option package for 440 six-barrel cars.
The interior decor code that you're thinking of is A87. This is the Road Runner Decor Group. You car does not have this either. Your car gets the black, reed grain baseline Belvedere interior with the bottom-feeder steering wheel. (Just like mine - except that mine is blue.) No rear armrests, and the stainless trim above the door panels and rear seat panels is painted black. Not polished - Painted black. Same for the armrest bezels on the doors. Black. Not chrome. This is how it came. Now if you want to dress it up a bit, well it's your car and you do what you want. No one on here will give you any flack.
I can probably take some pictures of what you need, as my car has all of the trim intact with the rear section of the headliner ripped out. It was hanging down when I bought the car and I just ripped it out. Maybe this evening - depends on how the steering system overhaul on my John Deere goes... :brickwall:
Here is a pic of how your interior is supposed to look. Not great, but all I have. Maybe one of the other post owners has exactly what you need...
Ray