Pop rivets have held hood scoops on hoods for many years in the past, however, with the quality of adhesives today, gluing a scoop on is the method of choice. 3M's 08116 and 08115 body panel adhesive will hold quarter panels on cars and some manufacturer's even go to greater extremes for the use of body panel adhesive.
If you do choose to use body panel adhesive the difference in part #'s I gave you in 3M is speed only. The 08115 and 08116 will give you plenty of work time to make sure your scoop is on straight and where you want it. I just checked my fastest 3M stock and the part # is 08147....this will give you a work time of 20 seconds and bond time of 30 seconds with total cure in 1 minute....much to fast for your application but, just to let you know how fast they can make adhesivesand there is a range of product in between the 1 minute cure time and the overnight cure time of the 08116...(Come to think of it I don't know what I would need to bond together that quick for myself or why I have it....must of been a sample from the 3M guy).
3M is an expensive product but, does work well, other manufacturer's also make adhesives that are a bit easier on the wallet like Norton, Dominion Sure Seal etx.
Hope this helps.