There are many different opinions on tires for Travel Trailers and 5th wheels. Below is the reason I stick with ST Tires.
ST Tires Versus LT Tires on Trailers
Here is what Goodyear says “Trailer tires are considered a special category in the current global design standards of Tire and Rim. The major difference is that trailer tires are required to carry 10% more load than an equivalent P-metric size tire. LT type tires are actually on a lower formula and would require a significant size or load change to meet the trailer load requirements.”
Also ST type tires are rated for a Max operating speed of 65 mph. Exceeding that speed rating can result in tire failure.
A switch of Load Range while staying with the same size will only give you more load capacity if you increase the inflation as it is the air that carries the load, not the tire. Info HERE.
Changing wheels to those that can carry the increased load and inflation to match the new tires is a good plan but what are you going to do about your axles and springs? They also have maximum ratings.
You can find links to most of the tire company web pages HERE