I like hte Pontiac one's better....let me see if I can find the webage.....
http://www.burnsvilleoffroad.com/01_09.html
To me here's what I am thinking, the Louvers would work great for venting heat out from under the hood, which is great, heat rises, the louvers point backwards, heat is sucked out.
With a front facing scoop you are forcing air down into the engine bay, hopefully right on top of your cold air intake filter, which is even better. If the scoop is large enough it would have the same effect as the louvers, except it would force the hot air out from under the truck, just like stock, it would just move more air
Then there is cowl induction which uses the swirling air at the base of your windshield to do both of these things.
If I add a scoop to my hood it will be for my ram air or cold air induction, so I am leaning towards a forward facing scoop of some sort, but on a hood looks are everything so the right scoop is critical. POrsche made some 944 Turbo's that have a SWEET scoop, also the Nissan turbo 300Z had a sweet little scoop for a few years, little square scoop, very effective. The Mazda Rx-7 had a massive scoop that fed the intercooler on it;s turbo but that is integrated into the entire hood. I think that Shaker hood setup is the best option of them all but I dont have the $$$$ for that sucker...............