Hmmm ...
My postwar 249 Scout-type has springs similar to that, though they bear up against the end of the brush. No holes.
I've never seen brushes with holes before. But then again, I'm a relative newbie to this old Lionel stuff.
Interestingly, Kane doesn't show hole-type brushes in his photo in Post #6, above. I see brushes with slots (#662), where the spring rides in the slot ... but no holes.
I wonder if the 662-type brushes would work with your loco ???
Hmmm ...
Do keep us posted on what you find out here. This could be a good learning excercise for many of us!
TJ