I'll jump in and add that the slot is not necessary as the CMC manual is wrong showing the slot way to low on the firewall.
I slide a small piece of 1/2" electrical conduit over the steering box shaft, align this against the firewall. this gives you a straight shot to the firewall column hole placement.
Bore a hole so that the top of the hole is approx. where the vertical meets the horizontal firewall area, make small adjustments as needed as the hole ends up slightly egg shaped.
What I do to fill in any extra you may have cut, make an aluminum retangular patch panel to slide over the column, (again be sure to cut the column hole egg shaped) add caulking between this and the firewall, set a few pop rivets to secure it in place.