The OEM Cougar shock is 1.06" longer when extended than the OEM Mustang shock.
The OEM Cougar shock is .69" longer when compressed than the OEM Mustang Shock.
The OEM Cougar shock has .38" longer stoke than the OEM Mustang shock.
Thanks for posting that. I appreciate all of the feedback.
I’m done with my shock absorber questions now. 
Royce wrote:“I don’t know. I use the Mustang spec Koni Rears, It is the same stroke / length as a KYB cheapie shock. Works great.”
It turns out that the Mustang (Shelby) spec Koni Rear shocks are too short. They were designed for a lowered Shelby.
The Cougar rear frame to spring distance is 1" higher than a Mustang by design. The Isoclamp system also requires more shock length.
When installed on a Cougar, they are extended nearly to the limit which leaves little travel room. I have installed them
using 3/8" fine thread stud-style shock extenders that have been rethreaded with a 10mm tap. However, the extension
creates a lever that can make the shock stud bend eventually.
Koni used to make Cougar spec’d shocks but they are obsolete. According to Koni:
Cougar Shock 82-1581
Max length: 465mm
Min length: 292mm
The closest replacement is an Aussie Falcon shock but they are also obsolete. 
Also, they are stiffer shock (1400N vs 850N @13 in/sec.
Aussie Falcon 80-2111
Max length: 488mm
Min length: 294mm
Thanks to Leon Bray for pointing me to the Falcon shocks!
Regardless, they work great.
Here are some comparison photos between an NOS C8WF Cougar shock and a Koni shock. The Koni shock has a about 1/2" less length at full extension. Compressed the Koni is about 1/2" longer.
Thanks for taking the time to post the pictures. I’ll probably just do what I did last time except upgrade the quality of the shocks a bit.