Ditto on what Dave says. Stainless bolts if possible, Kodiak SS brakes, etc.
There are plenty of locations to buy trailer hardware. If the frame is in great shape rebuild it. Lots of options as far as trailer parts companies, if you were closer to Tampa I could help you with parts selection in a minute.
Nothing to it, a 4 1/2" grinder with cut of wheels and the rusted parts are ready for the dump in 30 minutes. I've done five trailers and it's no big deal.
To get prices for comparison and information try these guys out.
www.sturdybuiltonline.com They also have some of their stuff on eBay. Oh yeah....this is where I bought my SS brakes a few months ago.