My Ranger an '87 STX 2wd came from the factory with one of those behind the axle bars and I kept it when I converted to 4x4 with a D35 up front...
I'd have preferred to switch to a later style forward of the axle sway bar, but I have a tow bar attachment frame and that interferes with installing a front mount sway bar...
"Sway bars" are somewhat misnamed, what they really are is Ant-Roll bars. and they have more to do with driver confidence than anything else.
a major truth that anyone who really understands suspension from a "Sports/performance car" perspective is that they make the suspension stiffer and the stiffer end of the car will slide first... So a stiff front bar will generate under-steer (which is "stable") and a stiffer rear bar will make the vehicle over-steer more (which is "unstable")
I spend a great deal of time trying the different sway bar thicknesses both front and rear to make my truck handle the way I wanted, as I understand the REAL truth about suspension tuning is that it is as much about making the driver happy as it is making the tires happy.
On the front of a Ford Ranger or Mechanically similar vehicles (Rangers(1983-97), Bronco-II, (1991-94)Explorers and F-150 (1980-96)
On these vehicles if grippy low-profile tires are installed and the vehicle is driven hard into a corner you CAN experience a "tuck & Jacking" effect similar to that experienced in the rear suspension of the Chevy Corvair.
The suspension tries to "tuck" under the vehicle until ultimately the tire loses grip and the suspension unloads, then the vehicle transitions into something race drivers call "SNAP Oversteer".
Years ago I was running 235/50-14 tires on my ranger at all for corners and my personal first experience wit snap over-steer happened...
After changing my underwear and taking a shower I replaced the drivers seat, and installed the stiffest front sway bar I could find and installed droop limiting straps on the front suspension.
Mind you I'm a previous owner of a 350SS-Nova, and several 340 Dodge Darts
As well as a 351-4V Cleveland Mustang, so I don't exactly scare easily...
You would freak if you went into a familiar corner in a vehicle you were familiar with and it did something unexpected that resulted in you doing an entirely unexpected 1440degree spin on dry pavement managing to sail between a pair of trees into an empty soybean field before coming to rest (thankfully still upright)
I am to this day still mystified why the truck didn't roll.
But I also set up my personal vehicles with a bit of predictable over-steer
because over-steer you expect will never catch you by surprise like under-steer that unexpectedly and suddenly unloads and transitions into over-steer
it is a complicated subject that can't be entirely resolved without understanding the personal preferences and skill levels of all involved
in the discussion...