Hi Casey,
A couple of thoughts come to mind about your trans shudder problem before you go all the way to solid mounts.
Depending on how your trans is now supported, it would be an easy test to order polyurethane blocks from McMaster Carr and just replace the rubber mounts you presumably have now. Like you said, it may be just enough to damp out the frequencies that cause the entire drive train to shudder.
Also if the way the car is shifted can "dodge" the symptom then you should look over the comments by Ian in:
slave cylinder
Changing the leverage of the clutch pedal (increasing the size of the engage/disengage sweet spot) made it much easier for almost anyone in my ZF car to always catch a smooth shift.
The CAV is a good car and it is easy to upgrade. Good luck with your project.