If it's a 100gs crankset (looks to be), the rivets are a softish alloy, and are possibly hollow. I've done this and it was as I described.

Roughly centered centerpunch>pilot hole>fat bit to decapitate rivets>sharp chisel to finish beheading if needed.

You'll be done right quick.

The now-exposed bolt-holes are standard and there are shims present, so look for them.

The de-ringed crankarms are bleedin' heavy, no?