You don't send in springs to my knowledge, I never did. I remove the springs first with a brake tool in a vise (bead blast the springs first in the open position so you can paint them black).
I had a 62 SS convertible that I sold -that had bad hinge rivets -would not stay up unless it was all the way up.
Restored new rivet hinges
will stop the hood anywhere you leave it between fully open and closed.
Have someone push up on your hood and watch the rivets for movement in their locations(the rivet heads or rivet ends should not move....) -not as good as the hinges with the springs removed since you can't check all the rivets for being loose.
Paul
picture of one of my restored sets- note the original style new rivets - Willie does not gold zinc plate.