the drive shaft in mine was vibrateing like hell, found out my u-joint decided to seperate, replaced and then a week later the vibes came back agoin, turned out i had to put a spacer on either side of the u-joint so it would sit level, now i just have to buy a new u-joint.lol
But yea, it could be caused by either on of the u-joints, or your carrier bearing.
Your truck has the same stance as mine now,lol
shackles,hangers,and coils, now i need a flip kit and drop spindles.