It depends on what kind of stacks you want. . if you want the good buddy chicken hauler stacks which have the rabbit ears, curving out, I would do 1. . if you have the Cow haulin' stacks with the 45° bullhauler cut on top, I would go with 2... just make sure you have lots of smoke and soot to pour out of them when you mash the gas! that is my favorite, seeing a truck with stacks, and the smoke pouring out of them as well! Just something to think about.
-Chris-