I need to know what the specification is for the input spline shaft on the Ford Cortina Mk III-V RHD manual steering rack. Specifically, I need to know if it's a 9/16" 36-spline like the Jack Knight racks, or if it's some OEM metric oddball that's close, but about 0.006" smaller.

it sure is!

This is a question I posted for someone on another forum.