HIS---
HIS username gives it away, not your username.
I'll help, as you seem to be a little challenged:
351-- stands for the motor that is in the car. Maybe it displaces 351 cubic inches? That is normally good. The engine is a very large contributor to how much power ones car makes, which brings us to...
coupe--in the Mustang world this mean's it's a coupe, or not a hatchback. You know, two doors and a wee lil trunk? Very light car, which is another contributor to relative speed.
Thanks for comin', now go have a seat and think before you speak, otherwise some smartass like myself will start all over again.
jfwy---welcome to TR, home of the keyboard hardass'