I have seen Shannons KOH rig up close and personal....believe me, his IFS does not even come close to looking like anything you will find under your VX!
Not sure how the rules work for the class you are entering...If your vehicle comes from the factory with some sort of traction device can you add a locker to the other axle and still comply with the rules? If so your VX has a limited slip in the rear so the best bang for your bucks would be a front locker (ARB or an Aussie with manual hubs).
Also I would definately beef up your rear links.