Cougar rear end question

I’ve had my 68 Cougar for 46 years now. It’s been mothballed since 1986 and now that I’m retired the time has come to restore it. It’s a solid car and basically needs paint and an interior. The question I have is will a 1969 Mustang rear end fit? Thanks in advance for your help.

Yes. 1969 Ford Mustang with either 8 inch or 9 inch rear ends, are a direct bolt in.
Your Cougar, if it has a 289/302, should have an 8 inch rear end from factory.
1967-70 Mercury Cougar and Ford Mustang rear ends all share the same width measurements and spring perch measurements if 8 or 9 inch.
8 and 9 inch rears even share the same axles if 28 splined.
1967-68 rear drums have 1-3/4 shoes, 8 or 9 inch.
1969-70 9 inch rear ends have 2 inch wide shoes.

Thank you for the information, just what I needed to read!