Just stay within the OEM's ratings and you will be fine...and use the best maintenance materials and schedule you can afford...willing to afford...
That is what any OEM's ratings/specifications/limits/etc are for...to tell you their customer the HOW2's of using their product...that they will stand behind it (know you know this Jeremiah...it for the lurkers out there)
Of course if in good condition and if worn, then the ratings go down. How much is the gamble trying to 'push it'... Plus, how the previous owner(s) have used it, maintained it, etc...
Differentials are pretty stout and one of the forgotten component systems...but here on a towing forum...a much more important component system
Daughter has my old 98 Mazda B2500 (Ford Ranger half ton) and has zero problems with it...other than the Michelin flotation tires cracking....oh yeah...SIL went 'stock' on their last brake set and it wore down to the rotors in about 1/4 of the miles of what I put on there.
They used to tow a Coleman PUP and rent U-Haul motorcycle trailers. Now that they are parents...no more track days till my grandson is much older...