Steering Coupler Question?

I have power steering in my Barracuda and I used to have manual. When I swapped to power I installed a power column I had picked up at a swap meet. My question is the power column coupler that attaches to the steering box is 3 3/4" long. The one on the manual box is 3" long.

Short of taking the column out it appears that both the manual and power box have a 3/4" diameter splined shaft and the splines count appears the same. My question is can anyone confirm this assumption?

The reason I ask is the new headers I installed come very close to the coupler and the shorter coupler would create quite a bit more clearance to the header. I can slide the whole column down in the mounts to make up the difference so the shorter length shouldn't present a problem connecting to the box.