Considering the V8 in the Cougar is almost identical to the Mustang's, I'd say go for it. It is much cheaper than you'd be able to get a Mustang for the same year for.

I've had a couple Thunderbirds from the same era w/5.0 motors and they were nice cars. Good for driving around, comfortable, and all the Mustang 5.0 motor parts will work on them, to an extent.

If its running, for that price its a good deal.