2000 Ford Explorer 4.0L Exhaust Manifold?

So basically I'm trying to replace the head gasket and I need to get the exhaust manifold off to do that. All the nuts on the top of the manifold are rusted on, I've tried everything on them, there's nothing more to do with them. The bolts on the bottom at the Y-pipe are not rusted on however I, again, have tried everything short of induction heating because that would be a few hundred dollars and this vehicle is not worth that much at this point. I've done PB Blaster, WD40 Rust, torches, freezing, breaker bar, impact, regular socket wrench. I'm not willing to drill the bolts out. (Too cramped and don't want to put more money into replacement parts.) Any ideas for me to help me get the bottom bolts off would be greatly appreciated.

Bottom of the Y-pipe? Can they not be cut off with an angle-grinder or Dremel? As for the bolts holding the manifold on the head, 'screw-extractors' may be your best bet. You drill a hole in the centre of the bolt (punch it first) and feed in the extractor in a drill/driver. It has a left-hand thread that digs in and engages, and your drill-driver turns it out.
Sorry, but I think that may be your only chance.

Can you remove the head with the manifoldl still attaches and then work on removing it when free off the car?

Sounds like you need a more powerful impact wrench. It may be easier to remove the manifolds from the heads after they are removed. One other possibility would be to start the engine up to warm it up and then shut it off before removing the bolts. An impact wrench will be the most successful at removing bolts without twisting the bolts off. My son was removing the wheels from one of his old trucks. He broke the first one with a break over wrench. He used his impact wrench on the others and did not break any more.