box car roof walks

[nw-modeling-list at nwhs.org]

Folks,
  What kind of roofwalks did the following N&W box cars have.
class: BS, B7, B8. I want to purchase some from plano  for future building
projects.
Thanks for any help!
Fred Mullins
modeling the Atlantic & Danville
remember "For Service See......the A&D!"