So, I found some speed nuts that worked. When I bought new DODGE letters for my Challenger hood, they came with zinc plated speed nuts. Since the original ones weren't zinc plated, I re-used the original ones. Those new speed nuts were the right size.
The issue is that the "pins" on the original top plate are tapered at the tip so the speed nuts will fit over them and start easily. The "pins" on the new top plate aren't tapered and it's more difficult to start the speed nuts. You have to apply some pressure while you turn the nut driver. The speed nuts I used had a shoulder on them so that I could put some pressure on them while turning. The original nuts don't have a shoulder so it would be pretty hard to start them.
