When I started down this road, I just wanted a class-8 tractor with a big sleeper "singled" for towing heavy tag along stuff. Interestingly, the gentleman I spoke to (some shop in Canada recommended on another hdt forum) recommended against a singled out class-8 for tag along towing, because there would not be enough weight over the axle for optimal traction.
That is what started me looking at complete conversions. Unfortunately, once I got looking at conversions, I wanted a motor home! Even though I now have the power to tow three of my boats, it is too doggone long to tow it. So, I am thrilled with my motorhome, but I still have to tow the boat with my pickup