I obviously never gave the driveline/pinion angle thing much thought for a street car as I had always heard of it in a drag racing, traction, blown u joints - driveshaft, context - but it may explain a lot. Took a quick gander under the car yesterday and noticed that the pinion has a definite downward angle (how much in degrees I'm not quite sure yet) but downward none the less. Also I changed to stock tranny mount, sub frame bushings, spring eye bushings, and rubber cushions under the spring packs a few years back all because the stock stuff was well worn and or deteriorated. After that I didn't notice that the vibration was much worse although it certainly didn't help to alleviate any of it and now that I think about it, it may have been a bit more pronounced in the higher rpm ranges at that point onward. If anything I just chalked it up to the newer and tighter rubber bits in place making whatever vibration there was, somewhat more more noticeable.
Regardless, I went out and found a cheap angle finder / protractor unit yesterday, as per the descriptions on the Team camaro site (can I say that here?) and will try and crawl underneath and measure what I find. The shims may be a bit hard to come by around here but it appears that I may end up needing some if what I see is true. I am very anxious to try this out as a possible cure to my problem. My car has always sat up more than many I had seen so maybe that is also something that has also contributed to the problem as it would seem to me that if the angles are off parallel, the sheeper the drivehsaft angle between the output shaft and pinion because the body sits higher, the worse the u joints would bind.
Thanks everyone for the whole other avenue of thought on this - sure hope it works out! - Randy