Honestly I don’t look at these trucks as towing machines by any means. For longevity purposes I’d avoid it personally.
I know not everyone is in the same situation but the newer vehicles are far better set up for power, handling and braking.
My 77 would pull my jet sled without a problem, though you could tell it was definitely under a heavy load. I’ve always read not to tow in 5th with these trucks also so driving at 80km/h or reving the crap out of it in 4th to keep 100km just seemed very inefficent.
In Europe most HZJ7x models where bought with the specific purpose of towing, most of them hauled 7500# trailers but some modified with air brakes could double that. I saw them all the time at 120 kph without any issues before they changed the law in Europe that stated you could only do max 90 kph when pulling a trailer. I have done many trips across Europe with a cruiser pulling another cruiser on the trailer and with the 80 or the 100 I would sometimes drive 130 to 140 kph for long stretches. Diesel cruisers are excellent tow vehicles , I agree with the new vehicles being better suited to tow as my wife's JGC with the V6 diesel will haul anything but I still prefer the long wheelbase heavier cruiser to pull.