So it doesn't wobble at 80 mph if you accelerate slowly to 80mph?
If it was a plain old balance issue it wouldn't matter how you get to 80, just that you're doing 80. It would be same wobble at the same speed. Same for the driveline, it would be the same wobble at the same RPM.
The fact that it appears only after hard acceleration is an indication that something is moving under hard acceleration. It could still be driveline or suspension related, but it sounds like you're looking for something that's moving under hard acceleration rather than just a static balance issue.
I agree with tooljunkie, you need to do a thorough inspection looking for cracks, loose or broken stuff. If this has been happening, you can even just look for shiny parts under the car because if things are moving around you'll see shiny metal where it's been moving.
