After three years of friggin around I fixed my vibration problem!!
I bought a LS1 driveshaft thinking that would fix my vibration. When it didn't, I assumed that the driveshaft couldn't be the problem and started looking everywhere else.
http://web.camaross.com/forums/showthread.php?t=536982
After an extensive search this summer I concluded both the LT1 and LS1 shafts must be bad. I sent my LS1 shaft to Dennys Driveshaft http://www.dennysdriveshaft.com/
He told me it was no good and built me a custom steel shaft for $350. ($400 with tax and shipping)
Problem solved. I've had it up to 120 with 4.10's, no vibrations.
$350 sounds expensive, but I bought the LS1 shaft used $160 shipped, 60 bucks for joints, $20 for a local truck shop to check it for straightness and balance (it tested good for them.....they didn't spin it fast enough) So i had $240 in a shaft that I had to throw away. Looking at it that way, $350 dosen't seems so bad for a custom made shaft spun to 6500rpm.....

 

Now that I am close to 400 RWHP I have been thinking about selling my 1LE aluminum shaft and getting a good steel one like this one.

Is the rear end noise any quieter with this shaft, many think that the aluminum DS amplifies noise?

 

Believe it or not, I used junkyard 4.10s from an S10 and they are dead quiet. So I don't know if the aluminum shaft adds noise.

 

Knew that had to be it Too bad that LS1 shaft was money wasted but at least now its fixed.

 

what was the initial vibration noise?

 

motor rpm has nothing to do with driveshaft rpm...its mph vs gearing just so you know...

glad yuo got it fixed it can be annoying my steel had a slight vib...swapped for a ls1 shaft and its good now

 

Actually motor rpm does have something to do with driveshaft rpm. For example if you are in fourth gear in a T-56 at 3000 rpm your driveshaft will also be at 3000 rpm and if your at 4500 rpm your driveshaft will be at 4500 rpm.

 

Just as an update.... I reinstalled my ES poly trans-mount with the preload plate, with no vibrations.

Also, I finally ran the car (only two passes before rained out)
14.02 @ 101.95. I need to learn how to drive. My 60's suck... 2.18.
I picked up almost 2 mph with the gears. Stock 97 LT1 6sp, catback, CAI, hurst shifter, 4.10's