Would they fit?
This is how the E500/500E engine bay looks like:
If you notice, the pic you posted (which is of an SL I believe) has the firewall behind the shock towers. To the rear of the airbox is that round gizmo with all those metal tubes sticking out from it. The airbox in your pic continues past it, with sort of "extensions."
I'm afraid the rear extension might not clear the firewall of the E500/500E, which has the firewall beginning forward of the shock towers. This may sugges that there is less space to work with. Besides, the engine bay of the W124 is shorter than that of the SL, isn't it?
Best way to find out is to get the measurements of the prospective airbox and compare them to yours.
Or you can always email MB in Germany. They'll probably reply in, say, oh, 10 years...
Hope that helps.