PLEASE change out those Axles!!! Mobile Home Axles are not rated / engineered for long term use. They are relatively cheap as they are meant to get the Mobile Home to site, and typically that is all. If these are the old style, they may even have spray painted on the tube something to the effect not for regular highway use.
I have seen these axles with the spider style flanges and they are a low speed axle at best. I had a car carrier trailer with these axles under it, and the trailer shop set me straight about the failings of a flange style hub set out.
For about 1500 a lot of shops will put a tandem 35oo pd set in with brakes on all 4 tires, re sprung, and aligned. If you really love the trailer that much, this could be a reasonable option. Better yet, upgrade to a new trailer if you can afford it.
Drewski