What do I coat my frame with?

[1970ChevyChamp]

Hey all, I am in the process of stripping down my 67 to frame, and I'm needing a quick question answered. What should I coat the frame with? I have seen them painted, but how durable is that going to be? My 67 isnt going to be a daily driver, but in the future I dont want any regrets because I went to cheap. Now having said that, this project is on a budget, so powdercoating will probably be out of the question. I have seen a buddy use the rustoleumn truck bedliner on his frame and bottom of his cab, but we havent seen any effects past a couple months yet. I thought for $7 a can it left a pretty nice, and durable surface. Any opinions on what I should do would be GREATLY appreciated. Thanks!