The link certainly has RST listed on it and refers to it as a trailer tire and the Goodyear site states they are suitable for trailers and 5th wheeels. I am only telling you what is stamped on my tires and there is no RST anywhere on the tire. It has the LT designation not ST.
I did not travel over the speed rating on my Marathons, I certainly won't be traveling over the speed rating of my G614's so that is of little concern to me. Inflation pressure and doing my best to avoid obstacles that will damage them has always been my main objective in maintaining my RV tires.