[kitcarbp]

Good photos, Roger is right, dont machine the input shaft splines so that you have less contact with the pilot bearing. I would keep it simple, focus on modifiying the pilot bearing to provide the step Roger mentioned and give it enough relief/step to allow the crank thrust bearing to have its proper clearance (fore-aft) so you dont wipe out your thrust bearing. What I cant answer is the exact clearance you should end up with between PB face and splines since you need to account for some thrust bearing wear over engine life( using the solid bronze PB Roger ref above). The TKO input shaft end play when new is 0 to .004", so thats minimal but should be accounted for its input bearing wear as well.

After looking at your photos, I now wonder if the TREMEC TKO 10 spline short input shaft kit addresses this issue? Could the 10 spline shaft have the splines far enough away from the PB? or are they in the same location on the shaft as the 26 spline shaft. The 26 spline is the stronger way to go in any case.