Educate me on what it takes to restore to stock

[AJLChase]

For those of you who may or may have not seen my past thread about a 67 pick up I had purchased that is 100% stock I am asking what is required to be considered a legit restore of a original pick up? Does that mean taking all of the parts that were originally found on the particular vehicle to be found and restored to like new or is it o.k. to replace with a NOS part or repop part? I am unsure of what is considered a resto and where it varies by authenticity or does it make much difference and who does it make a difference to? Many parts on my truck are solid and not totally rotted,cracked,busted or missing. But some are. Just need to know if I should rework them all or is it o.k. to purchase new?