1996 Chevy Cheyenne extremely fed up

I'm at my wits end. I've had this truck for 6-7 years now. And ever since i've had it, the truck has had a vibration/shake in the front end. I've done everything that I can think of, (all the u-joints, steady bearing, tie-rods, idler arm, pitman arm, intermittant steerin shaft - main/middle, and the top part, wheel bearings, balanced and rotated my tires - numerous times, nitrogen in my tires, different tires/wheels, rear brake drums, new front rotors, machined rotors) and there is more that I can't think of right now. As you can see, some of this stuff probably wouldn't help at all, but I just don't know what to do any more. Everytime i've each thing, it either fixes it for a day or two, or usually just makes a different shake. Can you help me?