73 spool trans mount/ Drive shaft Blues..

Okay guys, I looks like I'm at 47-5/8 CL U joints. (I measured from back of joints, see pics)
I stabbed it back into the transmission and it felt like a mile went in, I tried to mark a reference point but couldnt seem to get a consistent measurement (user error)
Also, I noticed my slip yoke had a groove in it, just enough to catch the finger nail.
Is this a telling sign of a bigger issue? (I'm pointing to groove)

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