Ron, you have to do the math as far as clearance. Check the clearance with your existing tires and find the dimensions of both tires and see if they will work. If it were me, I'd stay with the Marathons. I went to Goodyear G614's on our Bighorn only after finding a bubble in a tire and having about 12,000 miles on them. I haven't heard of near as many issues with Marathons as I have other brands of tires made in China. I don't know if they are made to Goodyear's specs or not but I think a reputable dealer would stand behind the tire if a problem does occur. Watch your pressures, do visual inspections often and while traveling, check temperatures every time you stop. Not for a degree reading but for a tire hotter than the others, keeping in mind that the tires on the sunny side of the trailer will be warmer than the other side.