This upgrade assumes you already have the main components for a 3018 to 3040 upgrade. eg 3018 Pro to 3040 Upgrade
If you use 450mm Linear rails, you'll need the "End Block"
If you use 500mm Linear rails, You'll need to cut them down - as they are hardened steel, you'll need a proper metal chop saw.
Line up the drilling template with the hole for the old linear rod.
I recommend you use M6 or M5 Bolts with the drill guides to locate them on the Extension Brackets and front/rear brackets and use a “Spur Wood aka BradPoint Bit” to drill the holes into the Connection Boards.
Make sure you use counter-sunk bolts as shown in the photos
I recommend printing the Mounts in ABS+ and 42% Cubic In-fill.
T8 Aluminium Lead Screw block from THIS “3018 pro SCV10VUU” kit
2x 2020 500mm aluminium extrusions (cut to size) - NOTE: I've removed the 2040 option as it causes more trouble than it's worth.
UPDATE:
I've added support for adjustable anti-backlash blocks as used by RatRig and OpenBuilds. These provide for much higher accuracy than the spring type anti-backlash nuts used on 3D printers.