To your original question, NOS or new? Neither. NOS carries a hefty premium, 3 to 5X lightly used equivalents. Since you plan to ride the bike, that premium disappears the moment you mount them onto your bike and ride.

Lightly used components are widely available, either individually (costly option) or in the form of a complete bike (low cost option). For the price of a couple of used components on ebay, you can find find a complete bike with those components and a lot more. Depends how resourceful you are?

Late 1980s mtbs go cheap, even high end ones.