Is there any way that you can put a 2nd gen spoiler on a 3rd gen??

Not going to happen without some major work...even then, I'm not sure. I've got a 79 Z28 and an 89 IROC and the measurements are way off. Besides, the 89's rear doesn;t drop enough to really make the 79 spoiler look all that good. IMHO of course.

You could always get the 5" IROC spoiler.

I tried this with my bird and after a few months of some shaving, sanding i gave up you have to basicall put it together for a one piecer and it is a pain let me find the pics i had of mine kinda sitting ontop of my bird. I personally think it would be easier to get the hawks 5" 3peice thats what i'm getting

just do a search for 2nd gen spoiler and my name you should come up with some stuff