Am in the process of replacing the tires on the trailer. Current tires (and the ones which came with trailer) are load range C and maximum psi is 50. Have been looking at the new Goodyear Endurance...
As to speed ratings...Provider tires have a proven record since 2010, and are speed rated to 81 mph. The Carlisle HDs also rated in the 80+ mph, and have been doing well for a couple years. The GY Endurance is designed similar to these, using a nylon wrap to allow cooler running, thus allowing higher speeds.