I echo johnsonbert's recommendation for stainless steel hardware.
If I might make another suggestion: Once you are sure you have the hardware in the proper location and everything is aligned properly, I might recommend that you put some Loctite Purple (or possibly Loctite Blue) on the threads of the screws. I'd remove each nut, one at a time and put a dab of the Loctite on it so you don't cause anything to misalign. Then, with the Loctite on, snug each one up securely.
Or, if you're comfortable with a rivet gun, that's fine too.
~Rick
2005 Georgie Boy Cruise Master 3625 DS on a Workhorse W-22
Rick, Gail, 1 girl (27-Angel since 2008), 1 girl (22), 2 boys (23 & 20).
2001 Honda Odyssey, Demco Aluminator tow bar & tow plate, SMI Silent Partner brake controller.