Wheel tubs for stepside???

[69c10step]

New here, seems to be a great forum. My first of probably many questions to come, does anybody make a wheel tub that installs on the inside of a stepside bed? Can a reproduction wheel tub from a fleetside be installed? Would prefer fiberglass, but steel would work. Trying to fit some wider tires under the back - figured a bolt in would be easier than trying to fabricate something.

Thanks for any suggestions and/or pics.

Tom