How wide are perches on a minitub?

I am curious as to how wide the spring perches are set at on an A Body that has the springs moved into the frame rails? I have a 72 Dart for reference. I tried a quick measurement of my frame rails, but wanted to check anyways for comparison (2nd guessing myself) as mine may not be to accurate, fully assembled and an arcing tape measure.
I want to get my new rear all set up prior to disassembling the car.