Need Advice, Suggestions

The tires are like new, only have about 500 miles on them.... the vibration was NOT there before the front end was rebuilt or the drivetrain was changed. It's going to the alignment shop on Monday morning..Also this
vibration is really bad, Is it possibe, just asking, that the shop that cut and balanced the driveshaft got it wrong?? this car drove really nice with the 273 in it, now its like riding in a cement trk...

Anything is possible. Could be anything from a bad harmonic balancer to a bad tire. I have had parts that were new that were defective. If you can access a set of jack stands you could jack up the rear end and place them under the axle. Block the front tires and test the car on the jack stands by accelerating it in drive just like you are driving it to see if the vibration is there.