I had to source one of these SL 3.5 clutch discs for a customer several months ago.

This is the one that I bought. It was identical the used clutch he had...

https://www.ebay.com/itm/Mercedes-Benz-280SE-C-300SEL-NOS-Sachs-Clutch-Disc/352418517754?epid=26014286920&hash=item520dc7d2fa%3Ag%3Auz4AAMXQHDlRcoao&_sacat=0&_nkw=mercedes+NOS+clutch+disc&_from=R40&rt=nc&_trksid=p2057872.m570.l1313.TR9.TRC1.A0.H0.Xmercedes+NOS+clutch+disc.TRS0

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David Hendy
'97 Renntech E60RS
'97 GMC 2500 Sub' Diesel
'95 E300D
'88 300TE
'88 250TD
'84 L/Rover 109