One of our late Mopar Club members had a '64 Dart GT 273/235 that he had put some fenderwell headers on back when they were popular. I was amazed at how much metal had to be removed from the inner fenders on that car! YIKES! Much more of a "race only" situation, rather than a hot street car, to me.
Header science ahs come a long way since back then! But if you're handy with a welder (for tacking and then full-welding) and have lots of time and patience, you can get a set of U-bends and some header flanges and build your own custom set. Time consuming, but it'll keep you out of trouble (with that project) for a good while. You'll need a chop saw, too.
My gut suspicion is that a good set of modern headers will fit better with less modifications AND be much more "livable" than the old fenderwell headers. AND make the same or more power, too.
Just some thoughts,
CBODY67