What are those things that are attached to the bottom of the front spoiler on an 87 Z28? Looks like you can screw something onto there? Thanks!

i am taking a guess, maybe part of the airdam..

Yeah, I don't know what they are for. I just switched my bumper cover from my 88SC for one from a 87Z because I was in an accident. They are on my 88 as well, but are tucked up under the front spoiler. These ones on the 87Z cover are facing down. They are rivited to the spoiler.

I've seen a picture on this site (a moderators car, I think), that had a semi-flexible skirt attached to the fixings. Not sure how the air dam behind it would have much effect if the air is being forced down the sides of the car?

on my RS, those are connected to an air dam/scratch guard.