Having had a class C of about that vintage. When you buy tires you need at least load range "E". When I got my coach it still had the original tires the ones that the chassis manufacturer had installed on the rolling van chasey. If I remember they were only "LT" rated. The previous owner had had several blow outs but had replaced with the same as original. I had a front one blow and replaced all of them with load range "E" and no more problems. The best thing is to weigh your coach(all 4 corners is best)and that way you know if you are within limits.
Bill