i have owned many 300s, NA you want a max of the 19 lb pph from the 302 and even then thats plenty unless he plans to rev that motor to the sky with boost, 19 will be perfectly fine, use the quarterhorse as thats your best option on that pcm, its located around the brake pedal assembly, that motor is really struggling with air, 4 pounds acts very differently than 4 pounds on a v8 like the 302, make shure you have a transmission that will handle the low end torque the motor puts out