I was thinking the same thing. Just an inch or inch and a half should make a dramatic change. I think the worst thing would be to add one of those aftermarket 2 pedistal generic wings you see on most '80's G-bodies.
What about changing the rear taillight panel to look like a 70-73? That would actually be a more involved process then that. You have to change the bumper, quarter and lower valence as well.....nevahmind