How to attach rear 28 Model A fenders to p/u box?

Does anyone have pictures or ideas on how I attach fibreglass rear fenders to a steel box on my 28 Model A Roadster Pick-up? I have the fender supports and brackets, but not sure how to attach the fender supports to the box. I think the originals were riveted. Can these be bolted or do they need to be riveted too? The box is new steel.

 

I believe the fender supports were originally rivited to the bed sides. That said, you can put them on the bed sides anyway you wish - maybe plug welding them from the insides to be completely clean for instance. then bolt your fenders to the supports.

 

Thanks for the quick reply...great idea!