^Well that’s a serious bummer that your brake setup is/was outdated.
In my experience I think most all 3500lb axles I’ve worked on had the same size bearings but it’s been a while since I’ve had any apart.
You do have the new part numbers or measurements, correct?
The OD of the races can be had off the specs on your new hub assembly. And the ID I’d the same as your old spindles.
Either way, if looking for a spare set, I’d just match up your new sizes( same or not) and get a new set, for 1 wheel. 1 inner, 1 outer, 1 seal. Parts are cheap enough. And it’s for an emergency replacement which if it ever happens is most likely going to be 1 wheel.
Good luck