1965 Pontiac GTO rear vibration and axle bearings going bad

I have a 1965 gto with an LS 2 with T-56 6 speed, moser 9" ford rear with 389 gears. I have baer brakes (track style) metco aluminum control arms (upper adjustable). I have a vibration around 65- 70 miles per hr. on up, never goes away. I have adjusted my pinion angle from +3 to -3. I keep going through rear axels bearings where the rear end grease penetrates the bearing. To stop the vibrations I have replaced the the axels, tires, rims, bearings, driveshaft, universals, center section, and housing. The t-56 tail shaft bushing is tight and there is no seal leak (8500 miles) No broken motor mounts. Drive shaft is balanced. what do you think? thanks steve