A-body Hemi box 4 speed

Someone have trouble understanding sequential logic.

I of course know Chevy would cut input-shaft, but to say he built this trans for his application is implausible .
If he built this trans, by the time he dis-assembly the trans (to swap main-shaft, supposedly), he would removed the input-shaft and have it machined.
He would not sitting there, in front the trans, with another invited guy back-and-forth the whole day hacksaw the input-shaft.

Now to the theory this is B-body swapped.

+ You happened to own 18-spline B-body trans from 1968 Hemi Charger or 1968 Charger R/T 4-speed.
+ This 18-spline trans happened to have build date by the time 1968 A-body SuperStock build : February/18/1968 and May/21/1968.
+ This 18-spline trans happened to be build from Assembly Plant that made all 1968 A-body.
+ You happened to have cast iron A-body tail-shaft. That tail-shaft have casting # match the time the trans build.

The probability for these outcomes happened at the same time is close to zero.
I respected a man of 40 knowledge, however, we do correct experience everyday, that is how air-plane, computer and spaceship were build.