The rear (tread) is narrower than the front (tread). I want to
make them the same. Is there a website to go to that custom
makes disks to bolt onto the hubs to make them the same ?
Google "Wheel Spacer" for about 1,600,000 references and websites.
There are many standard spacers - no need for custom.
Reversed rims could be used in the rear without spacers, but then
front and rear tires would be on different rims.
Any widening of the rear tread will begin to crowd the fenders.