You are limited to what is available in 13" ST trailer tires. When I went to replace the 4ply tires on my 95T, I found that they were only available thru special order. So I oped for the 6 ply. 70 miles per hour is to fast for ST trailer tires and especially old ones, sustained high speeds for an hour or more is inviting tire failure. I can vouch for this as I had many tire failures until I found out that ST tires have a max speed rating of 65 miles per hour. The last one that failed on the 95 was a over a year ago. The tread rubber came off the tire, but before it came off completely it removed all the gray and black water pipes and valves also put a hole in the floor, it was a 2 year old Goodyear, 6 ply tire and I was under 65 mph but the tire had been ran at 70+mph for several hours the year before. I now keep my towing speed at or below 65 and since the last failure, I have not had a tire failure in about 6,000 miles on new tires, the new 2209T has the newer 15 radials that have a nylon belt added to the steel belts, hoping they are better. Don't know if it is true but the tire guy told me that all manufactures of ST trailer tires with steel belts are now adding the nylon belt.