The torch and cut off wheel are drastic measures! Are you using a roll pin punch and a big hammer? If the engine is still in the frame, you need to work from underneath. I assume the area is clean, and you can see the spirol pin. grind it flush with the collar, then, use a proper roll pin punch and a heavy hammer. I've never failed to remove a pin this way.
http://www.amazon.com/Craftsman-9-43...roll+pin+punch
The next thing to do is drill it out with a solid carbide drill bit. drillsandcutter.som has the drill bit. That pin is 3/16 inch.
http://drillsandcutters.com/dmod316carbide.aspx
Cutting off the collar is a last resort and will require a weld repair.