When mine had vibration on acceleration it was the driveshaft (OR propeller shaft). The driveshaft carrier bearing is held with a rubber bushing that had become soft over time. No obvious signs until I had it up in the air and it had some play. Unless someone has come up with something new, The center carrier bearing is part of the entire driveshaft assembly and cannot be replaced separately.
While you're under there, replace the lower transmission mount at well. I replaced mine shortly after the driveshaft. It had sagged leaving some play. Play that may have contributed to the driveshaft bushing failing.