Pulling Engine/Trans over the winter....Header Question??

I run the 1 7/8 TTI's.
Only because you can no longer purchase the Headman Hustlers.
Tubular Automotive told me that their header would fit a 71 Demon but not a 71 Dart.
I didn't feel like arguing so I left it at that.
Lol, wow !
They really don't know that?