update - continuing saga
 

Sorry 1LOW03GT,should have been clearer re: Al driveshaft, it was balanced after shortening.

So back to the same shop for help. Found out the driveshaft that was shortened and balanced was still out (badly). While waiting for the shaft, put in Eibach springs, Steeda subframe connectors, Bassani mid lengths and catted X. Built a new Al driveshaft, balanced and installed. Problem is not any better, lost faith in this shop and their reluctance to pull the diff apart.

Began talking to local drag racing guru from waaay back. He is convinced the original install was bad (vibration on acceleration, none on deceleration, droning sort of humming resonance). Sooo, I am going to have him re-do the gears (pretty sure the wear pattern by now is f'ed up on the 4.10s) with a new set if the 4.10s are bitched. Might consider 4.30s now since I am doing gears twice...

Weird......I would've never thought that LOL!Hope you get this sorted out.You've got some good patience i tell you.
I think 4.30's would be a nice upgrade.This is something i've been pondering on for the last couple of summers myself.LOL!

I've never driven or ridden in a car with 4.30's. I've only ever felt 3.73's. Am I missing out?