What does this driveshaft fit?

[Lynn]

Or, maybe I should say, what did this driveshaft come out of?
I know it will "fit" my 69 Z, but I am pretty sure it isn't the original.

I believe the yokes are ths same. 3790024. Pics attached.

DS measures right at 50 and 3/8 inches from center to center on the yokes. Could be off a 10th either way, as I was measuring by myself.

I know it is about a half inch longer than the standard Z driveshaft. Also, the yokes are NOT out of phase as are most of the Z shafts. Finally, it did not have the three paint stripes. Only had one, and it appeared to be pink. It was not very visible.