91s have a different ACC system - separate recirc button with its own timer vs full ACC control of recirc.

Someone mentioned central locking. Either in 84 or 85 the 126 went to actuation from both front doors and the trunk vs just the driver door.

The console window swtiches changed in 86 so I think the wood panel and of course the switches changed. Might be possible to update an 81-85.

86-up knee bolsters make a convenient place to store glasses.

The door panels changed around 88 when the 126 got front door speakers. The panel lining went from perforated to pleated. I think it's all interchangeable.

I think the door and rear speakers were upgraded from one-ways to separates in 90. Maybe it was an option. Either in 90 or only in 91 the 126 got the silly Becker 1432 with the tuner in the trunk and amps behind the seatback. Marginally better sound, headache to replace with a sane stereo unit.

There's tons more but what was this thread about again?

Sixto
95 S420
87 300SDL