Technically to get this set up to work you would have to get the following goals achieved before it works:
1) You only need one engine to make the setup work, power is not going to be an issue here so any good availiable powerplant would do the work
2) You have to install a front axle in the back wheels to be able to make the wheels head in the requiered direction, no big deal here either
3) You need to install separate steering units for the right side and the left side in each axle so that they can steer independently in the following directions but check the alternatives that each demands and make your choice:
back axle is fixed in straight position and front wheels turn to the same side simultaneouslyas in any existing vehicle
front and back axle wheels turn to the same side that way the car advances forward or backwards to the right/left side in a parallel way to the direction of travel
[*]circle turning with out vehicle travel (0 displacement of its axis)
front and back axles turn to opposite sides so that wheels describe a circle when power is applied, this also requieres that the wheels turn in opposite directions in each axle
[*]short circle turning
front and back axles turn in opposite directions (both wheels in each axle turn to the same side) that way the vehicle describes a VERY short radius of turn like the ones achived by big rough terrain cranes, all the wheels turn in the same direction.
As you can see only the 0 advance option requieres opposite turning of the wheels and opposite rotation of the wheels, the other options are achieved very easily with jyst a second steereable axis in the back, just like the mentioned cranes, just make sure your back axle steering will be blocked over certain speed or a really dangerous vehicle will be in circulation.
4) If you spin by hand one wheel of a raised axle the other will spin freely in the opposite direction then you have two options either develop some type of locking mechanism that makes this "natural" opposite spinning work under load or in the opposite way make an UNLOCKER that lets one wheel in each axle to spin freely and then the turning will be achieved by just two wheels powered and the other two in free spinning position.
The rest of the vehicle is achieved by just looks, raised axles and big tyres which I have seen are much more aggresive in many member owned vehicles who participate in this forum.
If I had access to the parts I would try to build one here in Lima/Peru 'cause I have the facilities but no one scraps parts for Jeeps around here they are too cherished for that.
If someone out there thinks its worth it to make a try I will jump in with the experiment.