Rated tire speed - Can I get faster than 62?

[Goin camping]

No, I'm not a speed junkie. I've been going to Kingman Arizona and if any of you have ever driven I 40 from Barstow East you know the average speed is 75mph. When you get into Az the speed limit is 75m.p.h. for ALL vehicles. At 62 m.p.h. I am a rolling roadblock and have had more than one tractor trailer realize real late in the game that I was going a lot slower than he was. I'd like to remove some of this excitment from my life and go closer to the flow of traffic. Is ther a 15in tire that I can put on the A/S that is safe/rated for cruising at 70 through the desert in the summer?

[Beginner]

75 MPH towing a travel trailer is a bit much in my opionion, that being said running 10 MPH below the traffic flow is equally dangerious (if the speed limit is 75 MPH every one is running 80 MPH minimum). Earlier this spring an older couple was involved in a serious accident (both are ok now I understand) and they were running the speed limit and were passed by a semi that set into motion a chain of events that lead to the accident.
To the best of my knowledge, there are no ST or LT 15 load range D rated at 99 MPH or above. That is not to say there isn't any, I'm not aware of any(the Cooper Custom Trailer Plus has been discontinued).
That is why I went to the LT225/75R16 LRD Goodrich Commercial T/A.
Beginner