Header dilemmas- 67 Barracuda FB w/383

They can be found... but be sitting down when you see the price! Usually well into four figures for the pair.
I have B-body headers (the set that was used for the pics on BBD) on my car and they fit very well with only a couple little dents. But as noted, manual steering only. You probably could rework some of the tubes to clear a p/s box but then you might as well start with a different set anyway.
Are you dead set on keeping power steering? I have manual 16:1 on mine and do not find it annoyingly heavy (except when turning the front wheels with the car stopped). If you go to a manual box, it not only takes a lot of weight off the front end, but also frees up considerable room for header tubes. Just my 0.02 :)