Here is a clip from page 3-18 of the Honda 600 Coupe Parts Catalog
which you can download from here.

part number slip, in the bag

The tachometer end.
this end goes into the back of the tach. Remove the red plastic covering first!

The camshaft end.
This end connects to the camshaft end

The rubber bit that fits on the firewall.


Waiting for 42 years in it's bag for this moment!