Cutting brakes in the rear would be relatively easy to mod up....people do it all the time. 4-wheel steering isn't all that common, but you do see guys putting Rockwells or Dana 60 front axles in the rear of the Jeep, and setting up rear hydraulic steering. I know several people who have done that. But if you did have 4-wheel steering, I can't imagine that the knuckles and axle shaft joints could stand up to 100% of the vehicle weight coupled with that much horsepower. Maybe CTMs could hold (maybe) but everything else in the steering assembly would likely fail. So from that perspective, it's more likely cutting brakes that are steering that rig, since they wouldn't be burdened with any weight support.
But of course, it should be pointed out that the Jeep in question is whole lot more "dragster" than "Jeep" now. That'd be a shitty trail rig.....