I agree with jockos comments; go for it. I would put time into looking at real patina on our trucks to get it right. Faux patina can be overdone and done wrong. I've seen some trucks that look like they would have had to been laying on their side for 40 years to look like the finished product
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I would also suggest, if you are going to go for it, just to start with wetsanding the paint you already have just to see whats under it. Start slowly with a 400g(?) and see what happens. Most of these trucks have been painted at least once in their past.
Good luck, and have fun.