What lubricant or oil should I use in the differential of my Jeep?

I have an old 1975 2WD Postal Jeep with a Dana 44 rear end. The manual says that I should use Trac-Lok (limited slip differential) gear lubricant. I don't easily see this on the shelf. What am I looking for?What lubricant or oil should I use in the differential of my Jeep?
The Track Lock is an additive you add in addition to your regular gear lube. It comes in 4 oz bottles. You should be using 75w90 gear lube and 1 bottle of the additive to allow the track lock clutches to work properly.What lubricant or oil should I use in the differential of my Jeep?
When the manual suggests you use Trac-Lok it means you should use it as an additive. Trac-Lok is an additive to be used on top of your regular lube.
EP 80-90 with friction modifier. The modifier is an additive that comes in a 4 ounce bottle. You can get it at any Chrysler dealer.