But what will you print? This is a non-obvious question: you will have to first design the part using nothing but an existing and often failed (sometimes catastrophically so) original. It wasn't rare in those days for every car to be unique.
Of course you need someone to design it. Which is not as difficult as it sounds. But the once-off nature is a hell of a lot easier than "setting up a manufacturing line" as the OP suggested.
Yes that was a bit of an exaggeration. It's not setting up a manufacturing line from scratch, but finding the spec sheets and contracting a workshop willing to do a small run on the desired parts, which is not that easy.