Athearn trucks and the Weaver Delrin trucks use the same size wheelsets - Athearn will work which means the Intermountain metal wheelsets also work
Atlas O has their own (as most toy makers do) and even some of theirs use different axles. Theirs tend to be the longest axles. They sell wheelsets to fit.
You can use AThearn or IM wheelsets in many MTH and Lionel trucks - some are a little sloppy fit but still work.
NWSL has most variety of wheelsets/axles available.
