Just a couple of comments, the driveline is one of the prime movers in a vehicle. If you find one in the wrecking/junkyard, is it still balanced or were the weights knocked off? is it straight enough that it can be balanced? If you don't know then you will probably have to get this done anyway along with new universal joints etc. If you can get your present driveshaft shortened and balanced that cheap I would do it. This will go a long way toward reducing vibration and lengthening universal joint life.
