welding the stock open centre is the way for a cheap setup

rex's by nature are twitch as hell unless you get the alignment sorted for RWD only duties, it takes a bit, the guys down at wheels world are experienced in setting up a rex for RWD tho...

as for mech diffs, there plenty, just a matter of how much you want to spend really...

and get a cage, rex's are weak as piss, and you can visually see them twisting up when setup for RWD and slide only action...

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Jesus Built my car, Its a love affair, Mainly Jesus and my hotrod