Besides the width it depends on what your definition of fit means? Will it fit without moving the spring perches? Probably. Will it fit based on it's width. Yes, 1967-1970 were all 59.25". Here is some more data:
I would assume the spring perches are located in the same spot considering the spring widths are the same, the only difference (which doesn't change the rear or the perches) is the length of the springs themselves. Maybe one of the more "seasoned" vets can answer on if they have specifically installed one, but as I stated before it will fit, the only question would be is if you would have to move the spring perches.
Currently I have a 9" narrowed a couple inches on each side that has ladder bars and coil overs. I want to convert back to leaf springs with cal tracs down the road so I need a stock width housing and will buy leaf springs and all the other hardware. This car is going to see some miles and I want a better ride than the ladder bars give. I have rear disc brakes I want to keep so if a big ford housing from a 69 mach 1 cj will bolt into the cougar I should be alright.