Looking like an excellent fabrication job. Wouldn't be surprised if you don't find customers asking you to build them one when it's done.
Don't think I'd risk hot dip galvanising for fear of distortion, especially after all that hard work. Thin sheet metal doesn't like the heat of hot dip galvanising typically 600 deg plus.
Best bet would be to use a quality zinc primer, seam sealer and waxoyle where possible, should give much better corrosion protection than the originals. Keep it away from salt water as that's far more corrosive than fresh water.