you measure between front edge of the nose cones as one measurement. Next measure the center from shaft to shaft. I use the middle of the dimple in the shaft as a reference.

If you are at a zero toe both dimensions will be the same. If you are spinning out the measurement from shaft to shaft will be a little less than the front dimension.
Spinning in is the opposite.

I take it we should set up our I/O like this too??????

A drive is a drive. No matter if I/O, or Outboard. Same theory applies.

Thanks