I've done the shackle flip and the front hangers on mine with the drill, 4.5" cutoff wheel, mini sledge and a $10.00 Craftsman cold chisel. While this method SUCKS compared to a torch or air chisel, if you don't have those tools at your disposal, it still gets the job done in a fairly painless but time-consuming way. I did the first few without drilling the heads. That really sucked.
The one thing I can say is that if you drill out the center of the rivet head and THEN cut a cross in them, it gives the pieces of rivet head a lot more room to "slide" when you hit them with the chisel. It takes way fewer licks with the mini sledge to get the pieces to pop off. Your cuss word count will still be very high, though. Don't have anything to suggest for that. GM REALLY didn't want those rivets coming out. Ever.