Mustang offshoots 

1) 1967 Mercury Cougar (it was later T-bird based. The last one seemed Probish, but I am uncertain.)

2) 1979 Mercury Capri (original, then Mustang, then Mazda)

Of the 2 Mustang offshoots: The '67 Cougar was a unique Mustang based car. The 1979 Capri was too much like a Mustang.

Mustang offshoots by Gerald R. Ford June 11, 2006

Mustang offshoots 

A Ford Mustang based automobile.

Of all the Mustang offshoots, my favorite is the current Avanti. It was originally a Studebaker. Then it became a Camaro based car. When the Camaro became extinct, Avanti switched to the Mustang platform.

Mustang offshoots by The Mustang Whisperer June 18, 2006