i was looking at the aftermarket 91-92 rear aero spoiler on hawks third gen and i was wondering if i want to put it on my 1984 z28 will it fit or will i need to drill new holes for it?

Yes it will fit...and yes you will have to drill new holes for it...your talking about the BIG wing correct....yeah you take off your old spoiler....have to drill 4 holes for the new one...and bolt it one (there is a gasket that is supposed to go with it also) you'll also have to fill the holes left by the smaller spoiler you removed.