They have quite abit of interchangeability, the axles seem to be the
biggest difference, and they can be changed if you open it up and take
the spider gears off the new one and put them on the old axles. that's
what I plan to do at my next change as I have one with the tapers and
bolt holes and the replacement has the snap-rings. I cant get the
wheels off of the old axles anyhow. I've been running it without the
bolts for 2 years mowing, pulling heavy trailers, jumping small ditches
and spraying them regularly with penetrating oil and hitting
occasionally with a FBH, they might as well be welded on.