Here are pix of a Mark VII crank and an XK140 crank.
Both have the Woodruff key slots in line with the #1 and #6 at Top Dead Center. I would imagine this is standard orientation for all XK engines.
I don’t know about E-Type, but with XK120 the timing mark is on the flywheel, not the damper, so you don’t need any orientation on the damper when it is rebuilt, but it definitely needs to be re-balanced by drilling holes in the periphery.