I'am going through the same problem you are having where you get stuck on anything mildly slippery. Thats a problem with a 2wd dually and finding a 4x4 dually pre 99 is tough.
I did alot of researching and I have come to two choices the Detroit True Trac or the ARB air locker. I looked into the Detroit Locker and the Lockrites both good options but I really don't want to deal with the clanking banging and clicking. I do spend alot of time on pavement I also spend alot of time on very twisty highway so dealing with trying to coast through S bend curves etc wasn't what I was looking for.
If I was doing nothing but offroad work then a Detroit would prolly be my choice.
I looked into the ARB I really liked the idea of locking the diff when I need it and turn it off when I don't. The price of the ARB was a tad pricey especially for something that wouldn't be used daily. If the price of the ARB didn't cost a arm and a leg I think I would go for it because you have the full benefits of a spool and a open diff.
I read all the literature about the Detroit True Trac and it seems to give you the best of both worlds its a all gear limited slip
There are no rotten clutch packs to wear out and no special gear lube needed no chattering and from what I have read the True Trac actually works. The only problem I don't think they make one for a Ford rear axle where my truck has a Dana 80.
I did give the lockrite a thought I really liked the price
I also liked that I don't need to reset the gears so I can do the job myself. I also liked that if I didn't like the locker I could remove it and put the spiders back.
I'am still considering the Lockrite as it is the cheaper option it does give you true locker capabilities but the purists say its not as strong as a Detroit.
The only time you will grenade a rear end when you have a load on the truck and the wheels are spinning then all of a sudden the tires bite hard ie hitting pavement. For us dually owners traction problems exist with a empty truck where there isn't enough contact pressure for the tires to get a good bite. I have spun tires with 3 ton on the deck but that was in some pretty extreme conditions which was a forestry back road which are not the smoothest and can be pretty steep.
Anyhow to sum up the rambling I drove people nuts on TDS flipping back and forth on what I should do because 1 and 1.5 ton trucks pre 99 are 2wd which is what I can afford. A traction aid in the diff is the only choice I have so I did alot of looking into what can be done cost effectively. A 4wheeldrive conversion is very expensive and labour intensive or spending 30 grand plus on a 99 or newer truck isn't my cup of tea either.
Spending upto 1000 dollars is cheapest option for us 2wd 1 whee spinners