86 b2000 exhaust manifold stuck

Changing a head gasket but I can't get the exhaust manifold off. The nuts are off of both the head and the catalytic converter, but the oxygen sensor won't budge and I've already rounded one corner on it. I've tried gently hammering a cold chisel between the manifold and the CC and it seems to move a bit more than it did. I figured I could take it off with the O2 sensor still in, but if that's not the case, someone please let me know. The other I idea I had was taking a bracket off that seems to hold the CC in place, so I can pull the manifold away. Or is the manifold just rusted to the CC and I have to keep working it loose?

From my '88 B2200 experience: The O2 does NOT need to be removed for this. Yes, remove the bolts connecting the exhaust manifold at its bottom to the first converter.

Thanks! I attached a pic to be sure. It looks like it's just those three nuts. The metal gasket seems to have rusted the manifold and CC together, so I think I may have to loosen something else, since there doesn't seem to be enough play between all the bolts to free the manifold.

I've always removed the three bolts from the bottom to separate the exhaust manifold from the first converter, but you may find it necessary to remove the bottom stuff from the front converter first for best access. If you remove the bottom converter stuff, you may be able to remove the exhaust manifold and front converter as a single unit. I used hand tools for this, not an impact, but I'm in Arizona so not much rust.

Finally got it free. Had to loosen that bracket I mentioned, if it helps anyone else. Thanks for the help!