Idea? Yes. Real trucks don't have running boards:
Sorry, but I'm probably no help. Running boards I've seen are usually mounted to brackets and ironwork which is mounted to the frame rails instead of the body/cab. There may be a few attachments to the body work on some aftermarket units, however. Holes in the frame would not have to be filled. It would probably be easiest to just dive under the truck and see how your's are attached.