Duster Driveshaft length causing Vibration?

Yes, you should address the excess stick out by either replacing or lengthening the drive shaft first and then see how it drives. I would also inspect and replace the tail shaft bushing as needed. Since there's so much stick out, that whole front u-joint is wanting to follow an elliptical path, instead of just spin like it's supposed to. That's what causes the vibration. If you fix that, the vibration will likely disappear.