J Concepts J82. You'd need to convert/switch to a T4 then apply the J82 conversion. And then you have a 2wd 1/8th buggy which you can safely power with a 1/10th system.
However:
Its not that cheap. $75 for the J82 bits, and you either have to trade the B4 for a T4 or buy a new chassis, wishbones, driveshafts, shocks, turnbuckles etc.
Its not going to be very competitive. It will be light and fast, but all the opposition will be 4wd and that gives you a major disadvantage.