Couple things come to mind about this
First, the use of aluminum would not have been "random", GM would have had a very specific set of parameters that dictated the use of the lighter components...presumably for CAFE concerns. Will we ever know those parameters? Probably not. Either way, GM does not/did not do things by "random chance". Personal guess would be a combination of powertrain/vehicle gross weight/anticipated production numbers for a given combination.
Concerning the hood springs for aluminum or 'glas hoods...my thought is to reuse the existing spring, with less turns on it. Probably take a little trial and error, but should be doable with a little caution...and a large vise.