Jim Carter parts sells the running board "tread" patch panel, and the supports underneath the boards. I have repaired mine with these, it is tedious work, but it is an alternative to finding new boards. My past experiences at local swap meets, about 4 a yr in the DFW area, is running boards are kinda few and far between, Usually go for about $100 a pair, versus repairing the ones you have. Something to consider. Check out Woody Vondracheks web site, he has an photo set about repairing them.
Mike