I personally would go with an H if you have to have a crossover pipe. I dunno how much it differs, but in the Mustang world, the x was always described as raspy sounding... I have an H with no cats on mine, and love the sound. As far as the difference between the two, it will prolly not be noticable. I would do the H as it has a deeper sound to it...I've heard the thing about the H providing more torque and an x more horsepower...but I think its somethin like 2-3 hp....nothing you will notice.... But on the other hand, do you really need the crossover pipe? I dont have it on my 76 truck, and it runs fine and sounds fine....would it benefit from having one? probably, but I'm not willing to spend the money to have my current exhaust hacked up and pay for someone making an H to go in there.