Our vintage Roadmaster Wagon's wheels had rotted out from being out in the sun too much. I modeled a replacement and changed the design a little, to be one with a hub and spoke design instead of a solid wheel. The original wheels are made of such a thin plastic that it was kind of a pathetic design to begin with IMO. This one is much thicker in the hub section and you can control how strong yours will be with your infill settings and the choice of filament.

A better design for this wheel would utilize a bronze bushing or a ball bearing instead of just a simple hole. But I thought I'd try this out first to see if that was overkill. It's been over a year now and these wheels have held up well. The photo is of the wheels after more than a year of use. If I have to print another set because of excessive wear on the axle hole, I will come back and update the design to use a bushing or bearing.

You should be able to reuse your old hub caps and they will fit in this wheel, but I printed new hub caps because mine looked pretty bad. The only issue is the hub caps will likely be printed in the horizontal orientation and the tabs may be vulnerable to breaking because of interlayer adhesion being poor. You would have much more strength if you printed the hub caps in the vertical direction, but they will obviously need lots of support that way. Honestly, the tabs are not really needed anyway as you can probably make them fit tight enough to where they stay put with friction so even if the tabs break off at installation, it may still be fine.

I need to point out that I did not need to make new tires. The old tires were in good enough condition to reuse them. They are difficult to stretch onto the wheels, but they do go on. Soak them in hot soapy water first as that will make the rubber limber and slippery. If your tires are shot, you can try printing the Tire model I have provided out of TPU, but I don't know how durable that will be over time. Please report back what you learn from that.