Cutting A833 Input Shaft Question

If it has been shortened what do you think it has been shortened for and with an 18 spline?
I have no way of knowing.
Maybe you can use my previous drawing I posted and base it on a LA or B-RB engine setup to determine if its cut to fit in the crank converter hub bearing(?).

What's this MP chassis book you talk of?

Several editions have been released. You see them available on Ebay occasionally........
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A b-body aluminum case for some reference........
FOR SALE - RARE-Aluminum 18 Spline 308 Big Bearing Hemi 4 Speed Case and Tail Housing-Build your own Light Weight 4 Speed B & E Body