Manual column shaft issue

I don't know the exact difference in the 2 shafts but 3&3/4 sounds about right. Look very closely at the shaft. You'll find a pretty weld bead all the way around it where the final piece was put on it. Final piece for manual shaft extends a good 3 inches below this weld.
Collapsing a manual shaft for power steering application limits column collapse in collision. Is this a big deal? Not if you don't have a collision. LOL
Extending the power shaft for manual application is making the assembly weaker. How much overlapping length remains? I don't know. I know aftermarket vendors offer power to manual adapters. Some more expensive than others.