I know I'd need something to expand just a little to stay in the hole but not so much that it over expands and cracks the hole open. I'm going to stop by Dexter Autobody in town and check with them. See what they recommend. I've seen a couple of nice cars getting done there. I'm sure they'd be able to help. I'll let you know what they say.
Didn't bother with the body shop visit. I just started with a tiny drill. It went through the outer panel then into a hollow area. So I open the holes up and used the barrel retainers I had and the went right in. A little tight too so I know they'll stay. The 383 emblems went easy too. Just put a little paint on the ends of the studs and held it up to mark it. Then drilled and used the nuts from the hood letter on the back side. Next thing will be the hood pins.