Found a good thread on the HF trailer and mods for same:
How to enhance a Harbor Freight frame
It's meant for turning them into camper bases, but the general methods are useful. I like the one with mud tires - looks like spares for the tow vehicle!
It even has links to bearing size info, replacing the hubs with US-spec hubs, etc. Apparently 5-lug 1" axle trailer hubs fit Jeep Wrangler wheels.