You do not need coilovers with the 3 link. It works just fine for the street. If you get serious about track or autocross, they will help because of spring selection, ride hieght adjustment and a bit better shocks.
Pepe Borja, my vote is for the 3 link. The car will feel more stable in the road... and be WORLDS better if you find yourself in an emergency avoidance situation.
I rode in a bone stock 3 link car this weekend. stock front springs, stock mustang springs and shocks... and the car was a COMPLETELY different beast on the autocross course.
Put it this way... no kidding.. the guy was talking about selling the car because he was soo squirley on the course last time he was out. He just didnt have any fun in the car. It was way to unpredictable. After the 3 link conversion, he was ALL SMILES all weekend!
If someone is worried about the upper 3 link bracket due to HP issues.. you can simply have some extra gusseting to take care of that... but look at Phil's example.. Drag racing is as bad as it gets.