If you're really just trying to decide between staying wingless and putting on an '88 wing, there are other things to think about that may make your decision easier.
How's the condition of the paint? If it were my car, I'd be hesitant to be drilling through a good condition rear hatch to mount up a wing, especially if I wasn't 100% sure I wanted it. It's much easier to drill holes than fill them. Plus drilling holes through metal = holes with bare metal edges = points of entry for moisture = RUST. Do it right if you're gonna put holes in your car. You knew this, but I'm just emphasizing the fact.
How good are you with bodywork? I know installing a wing hardly classifies as bodywork, but unless you're planning on just swapping out the whole hatch from your parts car, it's kind of a one-shot deal. Either you get it on straight or you don't, and you notice how it's off by 1/8" every time you look at it. I'd be afraid to do it, but I'm not good at body work, plus I'm impatient. Of course this is a moot point if you are an expert or are just swapping the whole hatch.
Just a few things to think about...