[StuckinAz]

I bought a 64 Impala a few years ago with a carrier bearing, it too had a vibration and before I could locate it the carrier bearing went out. While replacing it i noticed they shortened the driveline to accomodate the updated tranny and the welded it back with no offset on the back end making it out of balance. I later found out they were buying carrier bearings by the bulk. Not saying thats your issue on the vibration but, keep it in mind and rule it out the next time your looking at it.