HONK HONK!!!
Here's the part number history for the '64-66 horn spring - which is helpful to find replacements:
Group 2.819
# 382116 --> 3896574 --> 3916047 Any of these part numbers will work
This is the same spring as '64-66 NON-Tilt Chevelles
Attached is a photo of the directions contained in the 3916047 part package.
Hope that helps!
