Google is your friend. 63-69 Comet 71-73 Comet 67-69 Cougar 62-73 Fairlane/Torino 63-70 Falcon 70-73 Maverick 62-63 Meteor 65-73 Mustang <!-- / message -->
As mentioned above, the eight-incher was under most V8 powered small-to-medium sized cars. I don't think it was ever under big cars or trucks. Some of those models also came with big-block power, and most of those got nine inch rears. Some six cylinders got by with smaller rear ends.
I have one under my 40 coupe running a 3 5/16" X 4 1/8" flathead I got from a late 60's Mustang. Never had a problem with it - and it is the perfect width.
montego under my A 1962-'70 Falcon 1964-'77 Comet 1969-'74 Torino 1965-'78 Mustang 1965-'70 Cyclone 1967-'72 Cougar 1962-'70 Fairlane 1970-'77 Maverick 1965-'74 Montego 1975-'80 Granada, Pinto and Monarch 1975-'78 Bobcat 1978-'79 Zephyr 1980 LTD II