Your best bet is to use something that either is, or is similar to, Overchan.

Unfortunately, Overchan is manually updated, as in, the HTML for the sidebar (frame) is handwritten for updates. This means tediously slow indexing, constantly broken links, and other such similar vexations.

On a tangential note, I wouldn't mind helping with a spider for imageboards. I swear, I hate the entire concept of toplists.