The big block Z bar is not the same as a small block one. Plus the ball stud bracket is big block specific also. The original bellhousings for '67 '68 '69 big block darts had a special mounting location for the ball stud bracket.
If you look here in the 4 speed frum you'll see a post where I modified a /6 Z bar to the big block dimentions. Plus I had to make an adaptor to mount my ball stud bracket to the Lakewood bellhousing.
I hope this helps.
Ted