It is not what you can do to a 2.5l block, crank, rods, and pistons. You can take all that and redo its entire design to get a better motor. But then, why? Cost to benefit ratio is not there. That is a major cause for not having a 'kit' readily and commercially available. No one has spent their r&d money into such a thing.
I question your enthusiam about shutting down v8 Mustangs. Its a Jeep vs Mustang. They are not the same in any way, shape or form. If you really need and want to shut up a Mustang, spend your money on a new Camaro or Challenger. Lots of bolt on products out there in the aftermarket to make each one compete. Why not take a Mustang V8/trans and toss that into your Jeep. Upgrade the rear axle, replace 4wd with 2wd (remove front 4wd axle for a straight 2wd drive tube axle), and go shut them down that way.