I use the IRS large ring diff and axle assembly. It requires 2 bearings for the pod/axle support, one bearing to support the spur and two bearings for the right side hub. It is very accurate and very smooth.

If you sand the disks like IRS recomends, you'll be able to run with a looser diff nut but still not slip. This will free up the diff a bit more and make the car turn more predictably and more efficiently.

Sands