Dual Snorkel cold air setup

Hey so I saw this and decided it was brilliant and I would try the same. Few questions though, how good is the seal against the underside of the hood clearance-wise? I found a 2 x 16" cake pan from Hobby Lobby and I'd like to use my non-drop base 3 x 14" air cleaner. My second question what are those rivet things to attach the pan to the cleaner base and where do you get them? I've never used them before...