I currently own a Jamis Aurora as my touring bike and I am not satisfied with the rear tire clearance. It seems that the largest tire the frame will accommodate is a 700x35. This is a respectable size, but I wanted to go slightly bigger, and I wanted to ask the experts to see if there existed any steel frames that are capable of doing the job...

I like the Jamis because it is steel. In fact, all my bike are steel except for my mountain bike. Anyhow, I wouldn't mind building up a steel vintage frame. I'd be transferring over all the components, so an English threaded BB would be a plus, but not mandatory. Anything 4130 (and preferrably lugged) would be okay by me. Can you guys think of anything?