X pipe H pipe or side by side
H pipe is more power and less money then a X pipe. below is a dyno sheet from someone that doesn't sell X pipes. Those who have them will never admit they waisted their money.
Think of it this way Have two hoppers hook up to an X. Flush them both at the same time and the **** will slam into each other.
Most will tell you the pulsation from side to side helps flow. Old school mopar firing order is 1, / 8,4, / 3, / 6,/ 5,7, / 2 this is the pulse not so effective is it.
H-PIPE all the way for old school mopar V-8's.