As you said, you already know about the motor mounts and the rearend, toss in the transmission and driveshaft to replace the torque tube and that covers your basics. You may have to move the radiator a bit or switch to an electric fan- I honestly can't remember if there are clearance issues with the "newer" I6 upgrades; though lots of folks here have done it and better than me will likely chime in to say things I've not remembered.