This is an easier question than most would suspect. First, lockers don't change the kind of gear lube needed and most gear lubes already contain the friction modifier required by a clutch-based LSD like the Tracloc LSD is.
So really, all you need is a good GL-5 gear lube that, if you have a LSD in the rear axle, simply includes words to the effect 'compatible with limited slip differentials' or similar. If you don't have an LSD, you can still run a gear lube meant for an LSD just fine.
Viscosity wise, use lower viscosities for cooler conditions, higher viscosities for warmer conditions or for towing. The exact viscosity used is less important in the axles than it is in the engine. 75W-90 is pretty commonly used, but 70W-80 is fine too in cooler areas. 80W-120, 90W-140 etc. for warmer climates or for towing.
I'd also recommend a NON-synthetic gear lube for the axles. It is coming out that the ring & pinion gears run cooler in a non-synthetic gear lube which helps pull the heat out better than a synthetic gear lube does. Some axle manufacturers like Currie have gone so far as to require their customers continue using a non-synthetic GL-5 gear lube in their axles to maintain the factory warranty.