ididit Right Hand Drive & Collapsible Steering Column: RHD 1965-66 Mustang - Manual (Page 3)

Now go under the dash and disconnect the wire
plug from the column to the under dash harness.
Remove the three screws that hold the gasket to
the fire wall.
Now you can remove the two bolts from the
dash mount.
(See Figure 2)
(Figure 3)
REMOVAL of OEM Column:
2.
Disconnect positive battery cable.
(Figure 4)
To remove the horn button on your
stock steering wheel, push it in an then
rotate counter clockwise.
Remove the nut and use a wheel puller
to pull the original steering wheel off
the original column.
(See Figure 1)
You will want to rotate the column left
and right to loosen and then pull the
column back toward the driver to remove
it from the car. There will still be a ¾”
round shaft sticking into the driver
compartment from the gear box. (See
Figure 3 & 4)
(Figure 1)
(Figure 2)