I'm doing my runningboards over and, in the process, found out all the bolt-kits sold are zinc-coated which means they will rust.
I went to Home Depot and all they had was galvanized stuff ... which will also rust, it just takes a little longer.
Finally I found a great source for all stainless steel bolts, nuts, washers ... you name it -- here:
McMaster Carr Thought I'd share the info.