Never on a car I owned/drove. This was in a cache of parts that my BIL was going to throw out ( he was cleaning out his garage prior to moving). It looks to be in good shape. Was complete with manifold, filter, etc.
Don't think that's possible w/o a lot of work. The M20 323i flywheel (FW) is only a half lb or so heavier than the M10 FW (which is ~13 lb). They come up for sale periodically in the E30 forums for $125-$150. I've got one on my E30 M42 and can definitely tell a difference from the M20 325i FW I had before. Of course the M20 325i FW can be shaved/machined down to the 13 lb range but that adds cost. Be aware that any swap from the M42 dual mass FW requires the use of the M20 323i TOB and M20 325i FW bolts as well as a late model M20 325i starter or a swap of the M20 starter bendix into the M42 starter.