318 or 360 Roller Swap

Stock the 360 is 245 horse. You will need the extra torque of the 360 to keep up with 4 speed auto and 5 speed manual 5.0 mustangs assuming you keep it stock. My 1990 Mustang GT ran 14.7 at 94 stock with 2.73 gears and 5 speed.

Even though the roller cam is more expensive you will have to replace more parts with flat tappet switch. You may be able to reuse the pushrods and roller tappets if you stay with a roller cam.