Car guys/girls, what should I look for In a muscle car I'm looking to purchase?

The other day I drove passed a very sexy vehicle! The body looked nice except for a few rust spots. I want it so bad, but I only caught a glimpse at it as we drove by in our beat up jeep. It looks like it could be a late seventies car, though my mechanical/vehicle knowledge is limited. What should I look for in this car to make sure its worth the buy?