That sounds like a good planFrom what I have seen is you have to use a big hole saw and cut a large circle out then weld the nut back on and weld the circle back in.
Can't quite do that, as I don't have access to a welder. However, I was able to use a step bit to put a small hole in the wheelwell side of the frame, get a small wrench on the bolt, and use a breaker bar (which required a LOT of patience) to remove the bolt. I ended up just replacing the very rusty nut-and-bolt pair with brand new ones, and tightened them as hard as I could. I finally got the front bolt off very carefully, and reused that one (It went back in MUCH easier than it came out). I now have my brand-new mount securely installed.That sounds like a good plan