It was a Mustang pickup and here’s the true story of how it came to be…True Story Of The Ford Mustang Pickup - 1966 Ford Mustero - YouTube
I’ve seen one. Here is a link and pictures. https://cccforum.discoursehosting.net/t/not-a-cougar-but-still-a-ford/1607/2
Steven
Yes have seen a few as well as a number of home made (rather than shop built) ones. Have also seen about a half dozen station wagons including the one Ford had built in Europe. Beverly Hills Mustangs did these pick ups as well as the continuation Shelby Convertibles. Always looking to make some money and and use up what seemed like a never ending stream of well used but normally rust free bodies available in Socal in the 80’s. If they had been into Cougars sure they would have built a batch of early Cougar convertibles 
Or something just as different
They also were one of the purchaser of allot of the Mustangs that were customized in the 60’s that remained in SoCal as well as movie Mustangs (often one in the same. Often pretty cheaply in the day though most have not kept pace with other more original versions.
Man wish I had not seen that!