Back of car vibration

Hi all:

Seems like one thing after another for me. first i had a heat issue, fixed that, now when i take it up to 60mph + I am getting a vibration from the rear of the car, the tranny was rebuilt along with the motor, the driveshaft was taken out to change the motor/tranny, and i drilled out the threads in the yoke of the carrier and installed through bolts/clamps from Jegs, with new ujoints both ends, I have 8 3/4 rear with 3.55's same setup i had before i re did everything, do you think it would make any difference to 180 the drive shaft?? the drive shaft was done in 1983 by a local drive shaft service. never had an issue before any idea's???