Oh... " 24 Hours of Lemons " explains it.

So yea, what Robb said-- the friction discs are the same diameter at 180mm but the early non-verto discs do not have the spring dampening at the center hub nor do they cost as much. I had a new pre-verto disc n my stock of parts and figured the best way to find out was to try it. Zero issues whatsoever.

Now, be aware that the later / revised verto fricton discs were 190mm. I don't know anything about cross-compatibility there.

Well I think Spank did mix them, and then we raced it in a MG Metro all weekend at the 24 Hours of Lemons at the Ridge in Washington.  Only problem we had was the left rear drum wouldn't release with an hour to go until the checker, so Spank disconnected that brake.  I took the checker on three brakes, with my best lap times.  Clutch felt fine, even after 14 hours of racing.

The MG Metro truly is an awful car, it was great.

I don't know either, but if I recall corrctly, the verto disc has the dampening springs there for a reason.. to reduce harshness of engagement, or clutch wear or something. BY "an early (circa 1982-- smaller diameter) verto flywheel" I think you mean that the flywheel's clutch surface is smaller diameter amnd probably the matching pressure plate too. Is the issue that you have the smaller flywheel and cluch plate and need a disk to fit it?

What? No one chimed in??  Must be because everyone is obsessed by "banning" someone!  Sorry I haven't even looked at that one! 

I didn't think the Verto disk would fit at all because of the sprung hub. I don't know about the other way, but why would you want to?

If memory serves, and friend and I once put a verto clutch disc in a pre-verto flywheel. I'm wondering if I can put a pre-verto clutch disc into an early (circa 1982-- smaller diameter) verto flywheel. I think the major difference between the two is the verto clutch disc has damping springs in it. CAn anyone chime in?