Figure it this way, assuming the intake manifold you are using is aluminum, if you could have gotten the same performance out of a cast iron aftermarket intake you would say "no way, im getting the aluminum intake, its lighter". On my '73 ranchero I saved 13 lbs. by making a lexan plastic rear window for it, Glass is heavy stuff, so long as safety is not an issue I say DO IT ! personally i would keep the glass windshield cause you can clean them forever and they will not scratch.