I built a trailer with MH axles about 4 years ago. 16' flat with additional 2-1/2' drop tail, ~~80" wide between the fenders. They hold the load of the trailer and my scrambler fine, and have run 70 mph loaded for hours on end. no problems. that being said, brake parts are apparently non existent. There are companies out there that rebuild them for the MH delivery services, but when I called Dexter Axle direct (maker of my particular set) I was told they would under no circumstances sell brake parts for them, as they were one time use axles. What is weird however is that they do sell replacement magnets for them. I think if you knew a friendly counter guy at ******* Tailer Supply or similar company, you could cross the shoes and hardware kits over to another set of parts, but I was unsuccessful in my attempts to do this. The bearings are standard stuff available at any good bearing house, and teh rear seals are available at NAPA. The next time mine need serviced, I think I am going to either swap axles to normal serviceable trailer type, or sell the trailer and build another one that is lighter. the first set of tires I used said MH use only on them, but the replacements I put on did not. they are rated for well over my load needs.
were I to build another one, I'd go ahead and use new Dexter trailer axles and be done with it, but at the time, my finances dictated otherwise, and it has served me well in the meantime.
HTH
Chad