Just an update from my original post. I ended up with the Maxxis tires, 225/75-15, in load range E. Have kept the pressure consistant (about 62 psi) and went to Nats and back last year (from Calif) with no blowouts. Have about 6k miles on the tires, looking good, so far I am very happy with them. I really agree with the recommendations to use a higher load range tire when available. Never a C load range. At least a D range, get E if available. Our enclosed trailer with car and stuff must be around 7k lbs, so I'm glad to find a decent tire!
edited tire psi, 4/13/15