It kind of depends on what type of box your planning on using. if your using a sealed box.. For a given output you will want the extra power a 2ohm configuration will provide.... However, if you are going with a ported box.. Then you could probably get away with the 8ohm configuration... Have you bought a 1 farad or so capacitor, if not.. I would buy one...
The only consideration i would point out to you would be the intended location of the amp.. If you are putting your amp in a trunk where it gets hot, you may have problems with the amp shutting down on thermal protection (wait, your in montana, does it even get hot up there?)... This use to happen to my amps when i had a system in one of my previous cars... Texas heat+high power amps in the trunk of a car is not a great combo..... However, it did allow me to verify the thermal protection circuitry was operation.
But, if you're putting the amp in the cab where it will be in the air conditioning.. Then, i say rock the 2 ohm configuration.. It doesn't really matter, as long as you don't over load your alternator which is unlikely...
