Not sure on the GN's, but not all WE4's had aluminum brake drums, only the non-posi ones from what has been gathered in another thread.
More confusion...
The whole back story to the WE4s creation is confusing.
One source attributes it to GM trying to slide under CAFE rules at the time (i.e. weight); the other and more plausible is that - GM, in their usual screwed up way, limited the GNs to no more than 25% of the Regal production volume.
Hell, I mean, you have to be sure to not make enough of the cars people really want and make more of the type people hate - right?
So, the WE4 was almost another example of Buick sticking their finger in Roger Smith's eye.
Remember him in the 80's?
The guy who deserves a lot of the blame for the trail of tears that became GM.
It was like - "Well OK, we will paint the bumpers black, and tweak it just enough and merchandise it as the Non-GN GN. Take that corporate!"
Besides; following the demise of the Buick G; many of the Buick engineers were either being taken our back and summarily shot (that's called laid off), or forced to go work for the collective. i.e The Borg at GM Corp Engineering to help develop more fine examples of badge engineered shit.
W car - I'm looking at you.
For 86 & 87 LC2 powered cars, I tend to see more 86 WE2's (GNs) with the YD6 & YD7 Aluminum bumper supports than 87's
Which is weird, since they made way more in 87.
The lightweight features of the WE4 were mainly limited to a Power Driver's seat delete (some debate about whether all WE4s had no driver's power seat), The Aluminum bumper supports; The N89 Alum Vector wheels, no rear spoiler (not much weight there); and the occasional non-G80 aluminum drums version.
And they didn't have the uber heavy Grand National emblems on the fenders and truck deck lid.
Mine is below