Those are nice headers, I like them, too. But the question was about big block headers and they can be a pain particularly with the bigger equal length tubes on a street car. Race headers (large equal length tubes ) belong on a race car. Smooth flowing, smaller heavy wall tube, compact design, easy spark plug and starter access, easy head pipe installation are what I want in a street header.
Sorry, I think that's the 2nd time I've done that. No idea on the BBC stuff. Does Dougs BB headers not fit as well/nice as their SB stuff?
The real issue is that the B and RB engines are physically bigger than the small block and in both cases you have to deal with the torsion bars in the car chassis (one of the reasons I am building a truck). One of the crate small blocks (440 CID) would be the best of both worlds, big internal displacement, compact external dimensions, light weight, easy spark plug access and plug wire routing. 
