It depends how much you love that particular truck (family vehicle...), but I would say mostly it depends on your skills and how much you enjoy/take pride in applying these skills to what may have been a lost cause.
Then there is the money issue (it is usually cheaper to start with a good clean complete vehicle) and the time issue (do you want to drive in 3 months, do you prefer to build or to drive).
So many parts are available that only a real complete wreck could be called dead for good.
But then again, if it is good enough for parts, isn't it good enough to rebuild?...
