I've tried many iterations and tried my hand at some pretty salty filament. This works, but I wouldn't print with it installed for very long. If you have some crunchy bearings and you're waiting for replacements, this could do in a pinch. I'm publishing my work in case someone has more ideas they would like to share and take it further.
OH, I almost forgot, you need (6) M5 x 30mm bolts since you'll be moving the concentric nuts to the outside of the truck.
5 shells, 5 top & 5 bottom - little hollow part is fine. I actually used Proto-Pasta's Conductive Filament in the end because it is mixed with graphite. Oh, yes, there are other uses for the filament than electrical applications.
If you're curious at the beige stuff in the bin, it's Igus iGlide J260 filament. It's the stuff they use on their linear rod bearings, so figured it would be the perfect stuff to use on this application. Well, it's a pain to print and not stiff enough to be the structural part of my model.