if you can remove all the rollers, plungers and springs then there is no real need to release the rivets, I have done loads of these, and they can be a real bugger to get out, as a last ditch if all else fails then I gas weld a rod onto the plunger, cut it down to about 80mm long and then heat the "socket" and wiggle the rod, that almost always works, but recently I had one where I had to de-rivet it, and drill holes in the back of the sockets, so that I could drive the plungers out (which I then found had no springs under them) I noticed several cracks in the cast iron housing which I would not have seen if I hadn't de-riveted the casing, (so maybe one should always do this for a look see) I had to bronze weld up my "removal holes" any way, so I proceeded to weld up the crack as well, upon which more cracks appeared,something that happens when you locally heat a small part of a cast circular item, it was scrapped, and a replacement was sourced, I had heated the whole thing uniformly before welding, it might have been prevented, but that didn't happen, and this was the ILOC chairman's bike, oh the shame, the shame, still it arrived here as scrap and was returned to him as scrap, so recovery was a failure on that occasion.
CLEM