Joe, first off, the 3 link does not make it handle bad on road at all. My truck feels great and I have the 3" rym springs. and Rym rear links. First thing I would do is wait till U get the rear links and install them. pick up an angle finder and place it on your rear brake drum. It prob will be angles down at approx 3 or 4 deg. NOw you want your pinion with your new rear links to point up at approx the same angle. You willl be able to adjust this with the spacers supplied by RYM.
Now take it for a ride. If you still get vibs you could remove the front shaft to see if they stop if they do, you could do the radius arms or the 3 link. Also, you prob dont need a DC shaft with that hight. You might be better off with the stock shaft. I would go with the 3 link cause it is adjustable and easy to set up. You also do that with an angle finder. My truck whips along at 70mph with no problems.
Legend in My Own Mind.