I've seen (and I can't remember where) a '57 with a 55/56 dash in it a few years ago. A few days ago, some one started a thread on the "other site" doing just that. I've been thinking about doing it myself. Yeah, I know my car is a long way from running, but I can dream, right?
I've always liked the look of the 55/56 dash and the available aftermarket options. Also, it seems folks wind up modifying the '57 column in some way depending on how they do their interior.
It looks like it's a pretty straightforward swap. I'm a ways off from being ready to do it, but almost have my self talked into it.