Originally Posted by CoastieCJ
While I've got the head off, I'm going to swap it out for a 4.0. If it can be done with the manifolds bolted to the head, I'll just switch everything over and then put it back in. The current exhaust is fully welded, so I'll need to cut it, put on the new 4.0 downpipe and then take it to a muffler shop to re-connect everything.
I'm sure working on the heads can be done without removing the engine but I think the problems you may run into will be:
1. Safely handling the weight of the heads while removing/installing
2. Completely removing the old gasket from the block (you'll be super cramped).
3. Replacing the gaskets and situating the heads without damaging either.
That said, I'm sure a number folks have done it successfully. I'm just giving you a heads-up on the issues you may encounter. Take your time, use the correct tools (hint: engine hoist) and be diligent and you should be good.
Best of luck!