Once you have broken the easy out in there, drilling it out is just not going to happen. Especially under the truck.

You can try the hose clamp, it just might work. At least long enough to get to an exhaust shop to have them splice in a new section with a fresh bung to mount the O2 sensor.

You could go to a bone yard and hack saw out a section of pipe from a rig with a good O2 bung welded to it. Then, get two adapter pipes at an auto parts store, cut yours out, mount the other one in, you are back in business.

Good luck.