Drive line Vibration

Was the vibration there before the restoration?

While the driveshaft might be too short have you also checked to ensure the exhaust isn’t making contact with anything (ie: gas tank)? How about the tires; perhaps a belt has separated or they are out of balance?

What condition is your transmission mount in? Rubber or polyeurothane? Rear drums balanced/not missing weights? Front wheel bearings are in good condition? Rear end has been checked out too (bad rear bearing or bent axle shafts)?