If you park your truck outside, the rain gutter will be wet much of the time (dew, condensate, snow, rain), even in Colo. If it's a garage queen, a slightly more rickety rain gutter might survive. You can buy repro gutter sections, but I imagine it's quite a bit of work to get a nice looking gutter out of those. I would strive for decent gutters, for the sake of the rest of the truck that is protected by them.
Colo Springs, CO