I replaced the axle on my 13'
Burro a year ago with a Dexter axle with electric
brakes. So far I've put 2k miles on it with no real issues.
The only small issue I had is the rubber plugs on the end of the self-greasing hubs were pretty low quality. Ordered replacements from Amazon no problem. I should note that I didn't want the self-greasers, but the axle dealer ordered them without my asking for them.
I opted to leave the old axle in place since it was leading and my new one was trailing. I just cut off the ends. I'm not sure if this was a good decision or not; my thoughts were for adding strength to the frame, giving myself a place to jack that wasn't the new axle, and lowering the center of gravity - though this does make the trailer heavier.
I would be happy to answer any questions you have.
'79 Burro, Rochester NY