Brent is correct about the stock Ford FE bell housing I am using. Checked it last night and it is approximately 6 7/16" (6.43") deep. Most all of the components in this installation are proven stock Ford parts. I did upgrade to a new steel 30 pound McLeod flywheel.
Here is the interference with the TKO splines with the pilot bushing. The transmission was not tight to the bell housing, there was a .100 gap between the two.
How much distance does a clutch disc require to float on the spline to relax and disengage?
The short (6.03") top loader input shaft was tight enough to leave a slight witness mark on the bronze pilot bushing. The pilot bushing is not proud as I first reported.
It appears that this input shaft is not the required short FE shaft that this installation requires. But I am not sure what Modern Driveline provided with my order. Do vendors re-manufacture shortened inputs by machining lengthened splines? Notice the two colors of splines in the above picture. Also, what is the purpose of the groove in the middle of pilot diameter?
Not sure what my approach will be with Modern Driveline. In a phone conversation, they seemed convinced that they had supplied the correct input shaft, but no way will this work without machine work, and that is not what I paid for.