Consider drilling about 1/8" into the head of the rivets with an appropriate size drill bit. You dont want to go too deep as to upset the hole in the A-arm. It makes removing the rivets a snap. Not much to it when you remove the material, after you drill part way through you can take a punch and whack it with a hammer and the rivets should push through. If that doesnt work just you can also attempt to hit the remaining heads of the rivets with a chisel and they should slide off. Again, just make sure you dont go deep enough to elongate the A-arm.