The hole is about an eighth inch tall and three quarters inch wide. They are pretty hard to get off without destroying them. They probably need to be replaced anyway though. Check out Team Nova at Novas.net Nova Chevy 2 Internet Resource
I use to visit it as I love Novas having had a 69 and a 64 years ago. I am not sure if it's still a real active board. But either there or Team Camaro Technical Question & Answer Forum - Camaros.net
someone should have a good idea of what brand "fuzzies" to buy. I know I had two different brands for my Buick and they both were junk. So get a good recommendation before you spend your dough.