I'm a fan of the helical gear type differentials (Eaton Truetrac) for the street, as they just seem to work and don't require any special additives or maintenance like the various clutch type limited slip differentials. I don't know how often you're lifting tires off road on a mild wheeler, but even with a manual transmission, a little heel-toe action, left foot braking and/or hand throttle pretty well handles that assuming this is all happening at crawling type speeds. Otherwise, ARB or Yukon Zip lockers give you fully open or fully locked, best of both worlds really, though I don't think the Zip locker is offered in anything less than a 35-spline unit, which then requires an aftermarket case with the Ø3.25" carrier bearings...not a bad thing and starting to look pretty strong for a semi-float 9" rear end. There are some complaints about the early 35-spline ARB unit for the 9", RD99, as the comp guys have pretty well found every possible failure mode on those units and then some, hence the RD99CE upgrade.
For my EB, I built a Strange N-case, N1905, with the Ø3.063" bearings and 31-spline RD119 unit, but haven't gotten it out into the wild yet. If I were to do it over again, I would have gone with the N1906 case with the larger Ø3.250" bearings, though my RD119 ARB pretty much means I'm running 31-spline axle no matter what. I'm only running Ø37" tires max, so hopefully I won't have issues twisting or breaking axles, but only time will tell.
