My '63 Belvedere has a 2-piece driveshaft with no center bearing. I've been trying to identify what it is, what vehicle it came from.

A large tubular shaft connects to the trans yoke, and runs about 3/4 the way back to the rear. At that point, the splined nose of a short, smaller dia. shaft slides into the forward one. This short shaft attaches normally to the pinion yoke.

What is this? Is it good, bad, correct/wrong for the car, etc. I'd appreciate anything you can tell me.

Thanks