How good are you with wood work and building things? If you are decent, you should be able to build a sealed or ported box(ported being a lil more complicated), but either way you should be able to build one for about 30$ vs. paying over 300$ for a prefab, or probably closer to 4-500 for a custom built ported box. Just go buy some 3/4'' MDF from home depot, look on kickers website for the recommended box volumes and port size etc...follow those specs and you'll be set. Depending on how much space you have, you may even be able to build the box exactly like kicker did. They show cutout dimensions for the box they built, but chances it are 2 ported L7 15's aren't fitting in your truck(not in the max box size anyways, and they would even take up a lot of space in a big SUV to go with the 6.0ft^3 per sub for max SPL. good luck.
