One thing to keep in perspective, is that as rubber ages (whether on a vehicle or in a box), it's loosing its internal oils and will basically dry out. When it starts cracking, there's no stopping it. PLUS, many of those parts have been laying around for a while so even though they have never been installed, the deterioration has started. Similarly, the NOS rubber parts are even older still.
A while back, in one of the Buick discussion groups, several participants were having trouble keeping motor mounts in their cars. They were getting either replacement mounts or NOS mounts. They all broke before too long (as they were not the later version of "fail safe" mount). Key thing was the age issue I mentioned above.
If drive shaft "whip" is an issue, there might well be some other issues that need to be addressed in the driveline. GM has used three-section driveshafts in some of their motorhome chassis with no real problems (similar torque, more weight, etc.). More vibration issues than "whip" issues, typically.
Each of the driveshaft joints need to be in a particular angular relationship to the other part of the driveshaft. Adjusting the carrier bearing assembly up or down with shims takes care of that, if it's been disturbed from the factory setting for whatever reason. I kind of suspect that a sagged rear spring set might be more critical than the carrier bearing height needing to be adjusted to get rid of driveline vibrations on heavy acceleration, for example or heavy loads. The service manuals cover all of those issues.
What CAN kill a carrier bearing is water intrusion into the sealed bearing. Typically, there should be metal water shields on the front and rear of the bearing. The metal shields might have disappeared during the life of the car "as they are not needed with a sealed bearing"--allegedly. BUT it was our experience on my Dad's '69 Chevy pickup that they are necessary and a sealed bearing isn't really sealed, or at least as some might suspect. Each year, after a dealership tech changed the ujoint and chunked the shields in the process, we had to replace the bearing. Then one of the shields got bent and rubbed a hole in the rubber insulator of the bearing. They got chunked again and it was a new bearing each year. Finally, we got some more shields and that was the end of that problem. Each one of those failed bearings, when the plastic "seal" was removed, looked like it was full of sand.
On those GM bearings, the rubber was replaceable as such. The bearing was a slip snap fit into the rubber and it all slid into the mounting bracket and then the whole assembly and the water shields were installed onto the driveshaft. Several different variations and shapes of the rubber over the years. Perhaps one of them might be adapted so there would be some recent manufacture rubber in the mix?
Back to the Home of the Forward Look Network