Chris,
A bit simpler than that, I recollect there is a hole in the crank end, for a spigot bush in the car I suspect, and a shaft that fitted snugly in there with a point on. The other part was a flat plate with a vertical metal bar fixed to it, this was used to mark the height, engineers blue, pointer scribed it, turn it round and align with the box. Could also be checked in the other plane. Going back over 30 years ago when we first did this!