* Transmission Mount Location: The transmission mount location is different between the YJ and CJ-7. You'll need to fabricate a new mount or adapt an existing one.
* Transfer Case: While the transfer case *might* bolt up, the driveshaft lengths will almost certainly be wrong. You'll need custom driveshafts.
* Exhaust: The YJ's exhaust system will not fit the CJ-7's frame.
* Steering: While the steering components might be compatible, it's important to check for clearance issues and potential modifications needed.
* Engine Mounts: While often the same engine is used (the 4.2L six-cylinder, for example), the engine mounts themselves may need adaptation or replacement.
In short: It's possible, but it's not a simple swap. Expect to do some fabrication work and potentially source custom parts. Many people do this swap, but it requires mechanical skills and the right tools.
