The gear needs to be exactly lined up with crank gear with the dots facing each other. The gear never changes.
Now for timing with flywheel thats different. And is lengthy as mentioned. Call Clone King.
Linked are two pictures, the first method I used, aluminum bore split, then clamped over gear by vise, use big adjustable on the web of the crank, gear will rotate with reasonable force. I made a set up that used the side cover bolt holes, an block made from a quartered cam gear turned inward, this was then forced with a threaded adjuster. I could change cam timing on the dyno with out removing the crank. That tool has been sold and I did not rebuild it.
Also on one of the engines on the bench notice the torque plate, I simply bored through a cylinder head, it replicates the bolted on head as accurately as I can imagine.
The keyed gears would be placed with the same accuracy, except there would be more machining operations to compound tolerance errors