96 Cougar began to over heat Mechanic says head gasket it has roughly 73000 mile

If a mechanic checked your car out and said it needs a head gasket it will be hard for any of us here to argue with that!!

What makes you think it is not the head gasket?

did the car ever overheat on u? also did the mech do a cooling system chemical test on it?

Mileage is not the only factor. The vehicle is 16 years old and age plays a factor in gasket condition as well.