Yeah its got some good info on that site but I'm not sure I belive its all accurate. I used to scrounge the junk yards constantly for 9" rears when I was racing dirt cars. This guy list a 54" housing for 67 to 70 Mustangs. I dont remember the housing length's exacatly but I remember the 69 and 70 rears were 60" track withs and the 67-68's were a little shorter, 58 or 58 1/2 if I remember right. He also grouped 67-70 Mustangs and 67-68 Cougars together. Why did he not include 69-70 Cougars in this group also? Its because 69-70 Cougars and Mustangs shared the same rear, just like 67-68 Mustangs and Cougars shared the same rear. And there differant between the 2 year groups.
Also he said the 71-73 Mustangs were the same with a 56" housings. He didnt mention 71-73 Cougars although they were the same as the 71-73 Mustangs. The problem I have with that statment is the 71-73 rears were actually only 1" wider track (61"
than the 69-70 rears although he list the housing as being 2" wider.
Maybe I'm mistaken about something here but I'm dead positve I'm right on the track withs.