I was among them who stated that it would be hard if not impossible, to install a two stage airbag steering wheel in a one stage steering wheel car from 97' but on the contrary, it is possible without getting any red airbag warning lights.
This is not a straight forward replacement but it is possible, by using the old clock spring, plus some modifications to the back side of the steering wheel by forming a new base for the old clock with an "aluminum epoxy" for the clock spring base, plus grinding/drilling and cutting a new hole for the plugs and wires and on top of that, you definitely need a new clock spring made for heated steering wheel, if you are going to put in a steering wheel with flaps. Hear are related pictures; #3 SSG/SMG Steering Wheel #4 SSG/SMG Steering Wheel #5 SSG/SMG Steering Wheel
A one stage clock spring is mounted on the steering wheel itself, but two stage is mounted on the steering column itself. These are to different type of steering columns and spring clocks, also the wiring connection plugs are different.
If this is done right, everything should work just fine, but with the sacrifice of loosing one of the airbag stages, so if it blows, you only get full blast in your face, instead of slightly less if you should get into a minor accident as the two stage was intended to work. I'm willing to accept a full blow and sacrifice the lesser one, not that I have any personal experience from airbags in my face.
My first try was plugging into stage #2, red warning light that I had to erase but was unsuccessful. Tried stage #1 and ones again, I got red light but it was easy to erase and now everything works, including everything else on the steering wheel. That took me by a surprise, sins this steering wheel has 4 extra buttons that where not on the old one.
This steering wheel is a little bit smaller in diameter and thicker in your hands and not as bulky at the stem, therefor it is easier to see the bottom half of the instrument panel.
If you are wondering what that thing is in the right corner of the picture? I had an old original BMW telephone holder that I added USB charger to it and a fold up stand/holder for my tablet or phone.
My latest steering wheel with integrated "paddle" shifter, seen inside the car; SSG-SMG Steering Wheel With Flaps in e39 from Feb.1997-/04.04.2021 and with the new Android display; 9' Head Unit