The fiberglass hoods are lighter than a steel hood. Trouble is, these trucks are very heavy anyway, so the little difference between a fiberglass and steel hood wont really make a big difference unless you start striping off a lot of other things. As for air flow, well the original cowl induction hoods were a hood that that in cold air to feed a big carb on an engine way back when. There are steel hoods today for these trucks that do allow air flow through the engine bay, and I have even seen some that have kits that will feed outside cold air to your TBI, but if you have a Vortec, the air going into the engine, has to be monitored. Truth is, there is no real need to add a vent to let out the engine bay air and heat. There is no real performance gain in a cowl hood on these trucks, unless you have a TBI, or a carb swap, and you pipe in the cowl so it feeds the throttle body, or carb, and can not pull any heat from the engine bay. A true cold air intake. If heat is an issue, your best mod is a good set of electric fans. This will provide much better air flow for cooling than adding a cowl hood will. I have a write up on here on what I did on my 97. Here is a link to my write up on the fans.
https://www.gmt400.com/threads/electric-fan-swap-on-the-cheap.41756/
If all you really want is the cool look of a cowl hood, I understand that, they do look cool, but it mostly just looks cool. It will help a little, but not much.
