It's hard to tell from the pictures, but if I was a bettin' man I'd say they were the Wild 1 Chubby 0508's. Here's a link to the Wild 1 customer bike gallery.http://www.wild1inc.com/roadkings.html
I found the techs at Wild 1 were quite helpful, what if you called them up, sent a picture and asked if they can't help you figure it out.
Here's another picture of a bike (mine) with the 518's:
They look like they may be the Big Johnson bars, they are very similar to WO518's but have a little flatter look to them (plus I don't think they have as much pullback).