HELP!!!!Put in 8 3/4 rear and it vibrates real bad

I did not rebuild it just new bearings. green bearing. It is a B body 8 3/4 out of 66 charger. In 67 barracuda. Had an 8 1/4 in it used same wheels and tires with no problems. It has a 741 case. Up front is 5.7 hemi with 545rfe trans. I have clearance on tires all around. I will put it on stands and try it.