What direction of subs in a Dual 12 sub box sealed for 1999 dodge ram ext cab under rear seat?

Hi Jeremy and welcome.
You might get lucky and fine someone here with auto sound experience, but this forum is really about pro sound reinforcement more than anything else (ie PA systems for bands & corporate events etc).
You might get more help at Diyaudio.com which I think has a car audio section.
Cheers.