8 3/4 rearend swap in 70 dart
On the contrary some versions of the brake lines will work from slant 6. I actually went crazy ordering lines from Summit to only return three of them to get the right ones once I remove my 7 1/4 rear the brake lines are almost identical and I could have used them.
I'm actually in the 8 3/4 rear swap process myself but with SS leafs added