YES Another mustang head question!!!!

Can someone tell me whats the difference between a cobra 5.0 heads from a regular 5.0. My cousin parted out his stang and he said the guy(WHO WORKED FOR FORD AT THE TIME HAPPEND TO HAVE A SET OF COBRA HEADS) well he rebuilt his engine put the cobra heads on his car ,but i took the heads off because the engine didn't fit in my trunk ,so when i compared my heads to the so called cobra heads they looked the same.does it have to do with different valves or what??????Not that im complaining because i got the engine for 160 with a performance cam and freshly rebuilt,but just wondering..CAn someone please let me know..Thanks