Supposedly, the complete valeo kit is 5lbs lighter than stock out of the box. I never got a solid number on how much could be taken off the flywheel just that there was plenty of extra material on it.
Cheapest I've seen the kit was $400. But it would be nice to have a low cost solution without any extra work.
I don't see why you couldn't use a 6 cyl flywheel. The getrag 250 was used on the 323/325 and I'm pretty sure I've read that people have installed m3 clutches on the m44.
Here's a thread
http://forums.bimmerforums.com/forum...Racing-stage-2 Seems like it should work no problem, just make sure to orient the clutch disc correctly.