I know this post is old, but my 2 cents worth:
I have towed a lot of heavy loads on the 14.5 tires and never had a problem. I have 5 on 5.5" disc type wheels, not the open center wheels.
Twenty years and only one flat from running over a bolt. The replacements are not easy to find, but they are available for $100 or less for a 10 ply tire. My tires are stamped "For Mobile Home Use Only" but no one in the CHP/DOT could find a reason to DQ them for road use. The Axles are Dexter, beefy as ****, and rated at 5k pounds max. each. They are not illegal in Sunny CA. and not dangerous.
I can sub Ford 15 inch diameter 5 on 5.5" wheels for the 14.5's, but I'd need to buy equivalent tires to keep the GVWR. If you dont like the hubs, measure the spindle and see if you can find another hub with the bolt pattern/wheel you prefer. Otherwise drop about $400 for 2 new axles and $150 each for new wheels with tires.