The Cobra II was basically a trim package on a standard Mustang, which in fact was not a Mustang at all but a Ghia-rebodied Pinto chassis. An anemic 302 V-8 was optional but was strangled by emission standards of the day. The car was loaded with the blackout grilles, scoops, spoilers and stripes that marked most American "performance" cars of that lost decade.
Still, in hindsight the cars seem appropriate to the times. The fuel crisis was dictating smaller and cleaner cars, and Europe and Japan were responding with very competent offerings. The seemingly impossible task of bringing the classic Mustang into the next generation was gamely taken up by Ghia of Italy (by then owned by Ford). The deep front spoiler, small hood scoop and louvered quarter windows seem directly cribbed from the '65 Shelby. The paint scheme sealed the deal.
Ford sold a whole bunch of these Mustangs. But the Cobra II's fell into a group of "sticker-pack special" cars (like '78 Indy Pace Car Corvettes, 1978 Dodge Lil Red Pickup Trucks, etc) that guys put away thinking they would be future collectibles- which never really materialized. So there are some very decent cars out there for very reasonable money.
Here are two offerings, on the opposite ends of the spectrum:
This one is a bit of a project, but has a new (and hopefully uprated) 302 motor in what seems to be a fairly solid body. A previous ad for the car asked $2500 firm and admitted to some rust around the rear window. At this point you have to believe the seller will take any offer. Nothing is worse than a project that is clearly upside down- and unfinished.
If you don't fancy a project, this one seems complete and ready to go. It strikes me as one of the aforementioned "future appreciation" cars that were well kept in hopes of a payday that may never come. This one has been for sale for a long time. I think the seller might listen to a more realistic offer at this point. There is no foreseeable upside to these cars, but they have a kitschy charm and can be made to handle and run better nowadays then they could in period.