How are the running boards mounted to the brackets? The PO bought fibreglass units but there are no mounting holes. How are they mounted to the front and back fenders? Is there spacers/bushings between them? How thick are they? A couple of pictures would be helpful as well.
Thanks

 

They are mounted directly to the bracket with short carriage bolts. I'm going to put a single stainless washer under mine so water isn't trapped in-between. I don't think it will allow the boards to flex, but if it does I'll take the washers out and let them lay on the brackets.

They are bolted directly to the rear fender (more carriage bolts). Again, I'm going to put just enough space between them to let water escape. Maybe the thickness of a thin stainless washer.

They are bolted to the front fender with a rubber bushing in between.

If your brackets are not exactly level, you can shim the boards up a little. Or you can shim the bracket where it mounts to the frame rail.

Below are the bolts according to MidFifty. Board to rear fender, to front fender, and to brackets.