Actually I have strongly considered doing both as you have suggested.
I went as far as buying a color-matching rear spoiler but after setting it on the car and studying "The Look", along with the need to drill holes into the rear deck lid, I decided against it. I instead mounted a large shark antenna for a different look that I feel does a much better job of allowing the twin humps to stand out best. The original rubber antenna seemed to be lost on that huge surface. I feel the large shark antenna is proportionately appropriate and required no mods to the vehicle itself. Of coarse it is a matter of personal taste.
I also looked into buying a Redline dual exhaust and rear lower skirt, but my restoration cost over-runs put a stop to that idea. Now and then a dual RL exhaust comes up for sale at the right price, but the seller's location never works for my Chicago area location. I still have my eye out for one at the right price (free would be real nice) being sold locally.