yes, it will definitely rust up. i'm building my own exhaust as well, and it's got a good bit of rust on it just from sitting in a dry garage. definitely gonna paint/wrap it at some point. out of curiosity, how did you weld your exhaust up? and that seat is pure style, i love it. some of those cloth wrapped spark plug wires like in that pic would look killer too! keep up the good work, i'm lovin' this thing!