I had a very similar problem. I tried heat, penetrating oil, a hammer, and finally vise grips, all to no avail. Mine were frozen so bad, the the *coin* base twisted off leaving the stud in the swing arm. BTW: This happened to both sides. I was determined to mount these rubber bumpers in the arm and removed the swing arms from the car so that I could get my drill press into play. I failed miserably at the attempt; the tops of the broken bolts were recessed in the casting and were angled such that I could not get a drill bit to run straight. So, I mounted the bumpers to the contact shelf above by drilling a relief hole and welding a heavy washer and nut to the panel. I filled my nasty recess (and nasty drill holes) with JB weld and filed smooth for a decent contact area. Okay, its not original but it works and I actually think it is a better solution.