You original 2 points were:

To cure a vibration, the front and rear flex discs must be replaced along with the center bearing.

A drive shaft removal is difficult for a DIY especially without a rack, partially because the exhaust needs to be removed.

My points: ( without malice )

While inspecting my _spare_ drive shaft I noted that the center universal joint didn't flex freely and felt notchy. I then went on to state that the notch _could_ cause vibration.

The center universal joint caps are retained by staking the yoke, something that is difficult using normal shop tools. I then asked if an aftermarket u joint was available.

In a second post I addressed that drive shaft removal wasn't an issue and gave an example of how GM used to lock caps and the field repair method.

( Again, without malice )