What were the other 2000S differences? I heard they had stiffer suspension. Were there any other interior or gearbox or engine differences?
A detailed spec may be known to some who have taken the time to research it thoroughly at BMIHT and by interviewing retired engineers, but as of a few years ago there was no consensus over whether the car was a higher performance version of the TC, or simply a higher trim level (similar to how Ford used the 'Ghia' badge in the 70s).
In terms of trim, I have read various reports of thin side strips (similar/same? as Federal TCs), a painted coachline, rear quarter panel in a contrasting colour, and wire wheels. Interior spec was generally understood to include leather-covered centre console (in same colour as the seats), perforated leather seats (as per contemporary Mercedes practice), wooden gearknob with 'wood effect' steering wheel, and a round dials instrument pack as per the later NADA / Series 2 cars. The instrumentation is possibly now debunked, but I haven't seen evidence to the contrary, whereas the James Taylor book explicitly records this instrumentation as 2000S spec and reproduced a photograph showing the instrumentation with a stylised 'S' logo on the dash end cover plate to the right of the Fuel/Temp gauge.
Theories abound over the mechanical spec, including power steering as standard, stiffer ARB, different spring rates and high-compression TC engine (with the 'standard TC' getting a lower CR instead). I remain unconvinced on the ARB, but PAS as standard would give weight to the theory that it was just a spec that had more options as standard. Alternative gearbox and final drive ratios may have been mooted, as the gearbox spec took a few years to settle down, and various hack cars were built around this time with alternative ratios... but I think the complexity of producing multiple variants en masse would have put the tin hat on this in production.
Given that most of the theorised trim items subsequently ended up available either on various export market cars (notably NADA), or as optional extras, I'm inclined to believe 2000S was just a 'fully loaded' trim level. If so, why not put it in to production? Well, they had enough on their hands meeting demand for the standard cars, and James Taylor suggests that the existing production complexities of producing all of the different export market variants may have made the 2000S spec an unwelcome additional headache on the production lines. But of course, that does mean you could easily build one today...
That's all I have...