I'd look it over pretty carefully before I bought it. Parts are hard to find, other than suspension stuff. If there isn't much rust, and the interior is pretty good, then go for it. It'* probably going to be a 4cyl or V6, neither of which is much of anything powerwise, but it could have a V8, although the late 70s factory motors are pretty turdy. A 302/351 swap is easy, but with anything over 250hp on a 4/6cyl rearend, figure on breaking it quickly.
They are great looking little cars, especially the Cobra II versions.
"I have a hammer! I can put things together! I can knock things apart! I can alter my environment at will and make an incredible din all the while! Ah, it'* great to be male!"