Ryan, You probably reached the limits of your drive shaft. You might try tom woods driveshafts. they are a mail order place and you send them your specs and the send you a shaft. Try looking in a mag for a number or a search engine would yeild something. Ive heard tom wood's is awesome.
Jeff, like I said, I don't have any problems with out the oveload or my old addleaf. Depending on how high you are, you might leave them both out. The overload will give you close to 1/2 and inch of lift and better tow capacity. If you tow at all or if you are low in the rear I would put it in. Also, the add-leaf could give you up to 2" of lift or only 1/2 an inch depending on age and condition. Also it will be stiffer if it is newer. The horizontal shock is for wheel hop. I don't get wheel hop, but I have the pushrod 4.0 and 33s with 3.73 gears, so I cant tell you if axle wrap will be a problem. You might try it and if it is, see if you can get a longer shock. You will have wheel hop and you might even get some breakage when you eccewlerate hard if it is a problem. Lets see some pictures of that truck!!
Zensuis is right on.
Also Jeff to answer another question, did you keep your new pads parralell to your old ones??? If they are then do you get any vibration?? If not then who cares wha it looks like, it works right! Oh, most addleafs are pretty simple and it doesn't matter which way they face. I've installed 3 sets and they were non directional and it didn't matter which side they were on.