Although I appreciate that it seems simple enough. I know that it is not. I am not speaking in hypotheticals at all. You definitely need both rear wheel speed sensors and they have to have the right tooth count and the correct calculations to get to the driveshaft speed being correct. Exactly correct. I sell tcm packages to about 3-4 people a year that have systems developed by other companies trying to do this exact thing. I think Roncallo's system works because he did it exactly the same as the factory.

And as I said nothing about what you described is cheap or easy. Even if he buys a donor car for 1000.00 to pull this stuff from it is tone rings and custom parts to get this all working and then hours and hours and hours of time stripping the wiring down. Rewiring and installing all this stuff in the car. You could just go get a part time job at Burger King and buy a really nice aftermarket ecu for around 1500-2500.00 and pay someone to install it and tune it in less time and money. Just a simple fact.
And when your DAS key takes a dump and your car wont start and they are discontinued you are SOL.

And S320s came with 722.5 from the beginning or near the beginning to 1996. So quite a few available in the U.S.