When I got my 265 in 2011 I pulled it with a 2002 Suburban 1500 with the 5.3L gas engine. No more than 10 miles from my house to the ramp at the marina where I kept it in a slip the remainder of the year. That truck was 'rated' for the weight (if the boat was mostly empty) but in no way did it feel safe or comfortable. The one hill I had to traverse required that I run up on the approach to ensure I made it. I'm sure air bags would have helped and I don't believe the trailer was properly set up for the boat (PO bought it just prior to the sale of the boat and the first time the boat was on it was when I put it there). The bigger gas engine would also have been beneficial.
For the past 7 years I've pulled it with a GMC Denali HD; 2500 with the 6.6 Duramax Diesel and can pass others while going uphill if the need arises. I believe the boat is better balanced on the trailer now than it was back then but this is also just so much more truck in every respect. Everything is bigger and stronger, power on demand and I'm much more comfortable towing in any conditions - though the width of the 265 still causes me to tighten my grip on occasion.
Ultimately it's what you feel comfortable with but having towed with both, in my opinion I'd say a 1/2 ton platform is the minimum and that's only if you're truly staying local, which includes local speeds. There's no way I would have put that first rig on the highway or gone much over about 45mph, not only do you need to get up to speed - you've got to be able to stop it as well. Would suggest the biggest engine you can get, I have no thoughts on the smaller diesels they're putting in those trucks, haven't driven one and don't know anyone who has one but they could provide a good power option.
Launching is another page in that story and I'd think would depend a lot on the quality and slope of the ramp(s) you use. I like having something heavy holding the rig in place when I stop on the ramp and at a bit over 8K pounds, the diesel gives me that.