A friend recently rebuilt his RanchWaggon and just used over the counter bailey channel. Was able to buy it in 6 foot lengths though he didn't use the channel with the stainless edge. We don't have quite the choice here in Oz. still looked neat when finished, unless buying from the States.
If you contact Ford Road Parts Store (Toby) I would be surprised if they didn't have an option for you. He is one of the founders of the crown vic assoc..