67 Cnet shaking/pounding violently

On my way to work today-a couple of miles down the road the Cnet developed a resonating sound. As throttle was increased so did the resonating. The sound continued to get worse and quickly turned into a shudder in the whole vehicle. (@30mph).
The shudder in a short time became a violent pounding of the entire vehicle and maintained at any speed over 10mph. The rear seat belts were airborn with the pounding. This would happen over 10 mph with the clutch depressed as well. (Just installed new pinion snubber-3/4-1" from plate last weekend and seemed to work just fine).
The engine/clutch/trans/u-joints have all been redone-last year and have about 500 miles on the drivetrain.
Any suggestions where to start looking?

Does it seem to be coming from the engine or from the suspension/wheels?

Check to see if you have some seriously loose lug nuts on one wheel. Check to see if the harmonic balancer is wobbling or if you have lost some weighs off of the flywheel if manual trans.

Check your front suspension parts and the front tires. This is not uncommon. May need to go to an alignment shop.

Got under it this morning. A cap from the front u-joint is missing, not sure how that happened as i am 100% that the c-clip was in place when re-assembled.