Not sure if it would be much different in a Ranger....
I run a locker in the rear of my F-150. Since I use the truck for plow duty in the winter, I wanted both back tires digging plus my front. And I wanted to make sure I had an easier time getting in and out of jobsites the rest of the year without having to lock in the hubs. I opted for a cheap LockRight at the time that I did it, it works but it makes noise and the tires will chirp and scrub at times. If I ever replace it, I'll probably cough up the extra money for a Detroit or E-locker. It takes a little getting used to because it does change how the truck handles in different conditions, but I'm happy with being able to spin both tires when I need to.
IMHO, I'd say go for it. I drove a Ranger around for years with an open rear axle and although with good tires it didn't do bad, I swapped a limited slip in because in the winter I often had trouble getting up out of the valley I live in. Before I got the axle it had been gone over and extra clutch disks added to make it work more like a locker. Only ran it a few months before a patch of black ice (and a bit of driver stupidity) put me into a tree though, so I can't really speak for how well a L/S works. My choptop has a L/S rear with extra clutch disks but that really doesn't count since it's a whole different animal, lol.