I'd get the Ford

Interesting ask.  Pros and cons to all 3.  For diesels, the Cummins Ram is the pick of the litter, but of the big gassers, I don't think there is one that is indisputably superior.

Ford: The "Godzilla" 7.3 is a relatively new engine, and I don't think they've sold that well.  There have been the usual teething problems that all new engines have, but I am not aware of anything major.  Only question is whether problems will start cropping up as they age.  (FYI: The TFL guys had one for a while and did a series of videos.  Might be worth a watch.)

GM: The 6.6 V8 is a beautiful engine.  Lots of power, fantastic throttle response.  But the cylinder deactivation system has had a lot of issues, mostly manifesting as lifter failure.  If you get one, be aggressive on oil changes and consider getting an OBD chip to override the "dynamic fuel management".

RAM:  Maybe the Mopar guys will say different, but I think this is an ancient engine. And I say that in a good way; the big Hemi has been around a long time and has most of the bugs worked out.  Ram quality has been suspect for quite a while, but their current engines are average to above average in reliability, and some people think they may be the only make whose overall quality is actually improving the last few years.

To be honest, if that was the decision I was making, I would go based on local dealer reputation as much as the truck itself.  Heavy haul trucks usually need warranty and recall work at some point, and you want someone close by that you can trust.

Welcome to the forum!

The 3/4 and 1 ton trucks are better made but I'll say go for Ford then Chevy/GMC.

I recommend test driving.

From what I've seen , The GM's have nicer suspension and give a much smoother ride than Ford, but they do get electrical gremlins.