*** WHAT THIS IS *** This is a tachometer needle replica for the non-Rallye dash, B-Body tachometer available at the links above. It's designed with a ~0.03mm shaft diameter (for the Chinese tachs that I designed the rest of the tach for) which - due to the limitations of 3D printing - will probably need to be drilled out with a mini drill bit and pin vise.
It's also possible that with some drilling this could fit an original tach, but I can't guarentee it.
*** NOTE *** You will have to paint the needle; it comes in a clear 3D printed material. I tend to lightly sand this material with Mr. Surfacer primer (though any auto enamel primer should work), followed by orange engine enamel paint.