I had the very same issue as you, with my "Triangle" brand tires, with 10K miles and 5 years on them. I was ready to change them anyway, but this forced the issue. When I took it to the tire store, they said a second tire was also delaminated very bad, and a third had started. I replaced them with Carlisle HD 235/80-16E, which has a speed rating of 75mph. It seems different sizes have different speed ratings. I won't be towing that fast, but I like having the margin.
Many people say put this or that G rated tire on. I didn't want to have to replace my wheels, to put tires on that were overkill for our 13K trailer. I couldn't go bigger tires, I don' have the wheel spacing. And I had read enough about the difference between ST and LT tires, that I chose to stick with ST. From what I've read, the newer Carlisle tires haven't had any issues, and they surely will be better than my Triangle tires. They look 200% better too.
That's how I made my decision, for what it's worth.
Mark