“was there a Mercury version of the Mustang?”
The Cougar.
I can’t remember ever seeing one, but the name is familiar, and it makes sense:
Mustang :: Cougar
Pinto :: Bobcat
Wasn’t there a Mercury Lynx? What was its Ford analogue?
No, the Cougar was the Mercury analog to the Thunderbird. It was related to the Mustang early on, but even then it was bigger, heavier and less performance oriented.
A long since sold pet project car of mine:
http://www.flickr.com/photos/tysonneil/sets/72057594110045799/