"Instead of a puller, I heated it gently then drifted the unit out of the collar. "
The puller won't move it so I'll try the heat and drift next. As I mentioned, hours of fun!
It can be difficult to get a puller set up right as there isn't much room under the collar. It sounds as if your unit has a properly tight collar (which is good). My logic was that if the collar is a shrink fit on the shaft, a bit of heat and some judicious drifting should do the trick - which it did (make sure you have a pile of old rags to catch the bits as, from memory, all the bits and pieces tend to fall out).
As for rivets, I ordered some, measured them against the old rivets, cut them down then tapered the ends (they can be a bugga to get through all the plates and the fibre gear - the taper helps).
In hindsight, after repairing about three or four of the blighters, I opted for the new one from Bergs (

). The reason was that most of the one's I bought were very worn and didn't look that reliable (and weren't). The one that disintegrated prompting the engine rebuild actually lost one of the posts the bobweights move on - you can imagine the carnage (it was wedged solidly in the inner timing case!!)
Andrew's instructions were absolutely invaluable!!