I too am partial to the Advance Design trucks. There are some models that you don't see very often, so it is possible to build something, if not unique, at least unusual. For instance I've never seen a canopy express except in pictures. They seem rare.
I have a 55 1st GMC Suburban. They are not common, but I know other people who have exactly the same thing.
I think it really comes down to what you care about. Build one that you are interested enough in that it can sustain your interest long enough to finish it.
Everyone here has an opinion, but I think we'd mostly agree that your truck should be your truck.
