This forum focuses almost exclusively on the 500E/E500 and the 400E/E420. Some tolerance is given for general W124 topics, particularly if the subject is in common with the above-mentioned cars, which almost everything except the suspension and powertrain pretty much is. There's also a small G-wagen forum, but it is not much to behold.
Anyone is welcome to advertise or talk about non-W124/500E related topics here -- they must just be relegated to the Off-Topic forum. I would recommend W140-specific forums such as Benzworld etc. for advertising parts, as only a small group of our members own W140s, and they are not discussed here really in terms of repair or parts sales unless (again) the part, such as the M119 engine, is shared with the E500E.
You would have MUCH more access to a ready market if you posted to the Benzworld W140 forum, or perhaps to Facebook Marketplace where more W140 owners live.