I feel you might be over thinking this.
I can't imagine there is any v8 1500 that couldn't tow your boat with ease. If it exists I would stay away from the brand all together IMO.
To simplify it: Longer wheel base, more power, and higher number gear ratio are the three main factors, but again any newer 1500 V8 should have no issues towing 5-6k. Trim levels typically have nothing to do with tow capacity, only payload.
You should avoid most brands then.
From the
link I posted above.....4wd, 4dr, short box, 1500 class, 2015 model year.
Ram - 4,190 to 10,150 (V8's start at 8,000)
GMC/Chevy - 5,600 to 11,900 (V8's start at 6,200)
Ford - 7,100 to 11,500 (V8's start at 9,000, Turbo V-6 starts at 7,600)
Toyota - 6,300 to 9.800 (V8's start at 6,300)
Nissan - 9,200lb (These are listed really wonky and separately, Don't want to dig through them all)
Towed weight of a 242x is 5,700lbs
3 "average" people in the cab is (3*178) is 534lbs (tow capacity assumes 150lb driver I think)
Misc Gear and doo-dads is 300lbs (Coolers, Ice, Beach Bags, spare cover, etc)
Total weight beyond curb weight is 6,500lbs......300lbs over the lightest rated GM, and 200lbs over the lightest rated Toyota. I would want a 10% margin myself so a 7,150 rating would be where I would shoot as a minimum for the heaviest Yamaha.
It's pretty clear that getting just "any V8 fullsize" can lead to weights over the limit without much effort. It's worth the time and energy to make sure you get one with the right setup for what you intend to pull. Yamaha boats do have the benefit of being significantly lighter than others. Some of the 24ft wake boats are sneaking up on 7,500lbs towed weight. Those in a 1500 class definitely require the right setup. Also, 7,150 happens to correspond with 500lbs tongue weight (assuming a properly setup 7% of tongue weight). This probably puts you into a
Class 4 hitch rating to handle both the tongue weight and the non-distributed weight of a boat trailer.
Wasn't intending to go into that level of detail, kinda got away from me. Also, my thought here is education. I was in the camp of "any 1500 will be fine" as well until I started to really look at the numbers involved.