In my opinion a truck is ruined when-
1. It is so modiefied it is no longer original(i.e. 49')
2. When it is not used, its a truck, trucks are for working. What I really mean is that if it just sits for no reason but just to look at, its a waste.
Those are my two opinions, mods are cool but done with taste and not going overboard. I have a duel carb setup but I still have the same engine and everything else is original.