I don't know what is called for in that box, but there are a few different brands of lube available for manual steering boxes. I've been using J-D cornhead grease and no problems. I made a nozzle for one of my grease guns, and pump it into the box until it's full. Nice and easy. And no leaks!
I would only get it about half full, not all the way full....but either cornhead grease, if you can get it, or another type of 00 weight grease will work. Can't find cornhead grease in the desert, so I got some 00 grease at Tractor Supply (yes, we have tractor supply stores, but no implement places)
Wondered what Cornhead grease was, so Googled it. Its what I know as liqiud grease. Just checked on 00 grease, now I know what to advise if someone asks what to put in a leaky steering box. Learn something new on here everyday.
I haven't re-did the steering gearbox in the truck, it tracks straight as a train on the highway which is nice, though 90wt gear will not stay in it particularly long. I switched to STP, it is easily found just about anywhere and seems to stay put. Picker head or corn head grease is known as "self-leveling" grease. NLGI #00 was not available on the rack at the local NAPA sort of surprised me, but maybe not as there really isn't an automobile application. NLGI #2 grease, used for chassis lubricant is said to be too thick, and will "channel" away from the parts that need to be lubricated in use. The Cork sniffers of course, will only want the officially consecrated Special Bespoke Fair Trade Manual Steering Gear Lubricant.