Is the bearing making noise or are you just getting the vibration? Also when do you get the vibration, all of the time or only when letting off the gas? If the vbration is only when you let off the gas, and you feel it comming through the it is likely your pinion angle is off do to the lift. If the vibration is all the time at all speeds it is likely to be u-joints-sounds like someone is hitting your driveline when you take off or back up, or the center bearing. If you are going to do the work yourself, it will be cheaper to replace the u-joints and center bearing(but a PITA for the center bearing). If you are going to pay someone to do the work, it will be cheaper to have a new one piece driveline made. I have one made for my '90 X-cab about 10yrs ago, and I haven't had any problems with it yet off road. You can see where I have spun it next to rocks and packed ice, but I haven't bent it yet.

If you do decide to have a 1pc made, E&J Engineering in Auburn does quality work. When I inquired about getting a second one made for a spare I was told it would run about $300(same price I paid for my original one)