'65 dart 318/904 7&1/4 daily driver. rear springs were extremely sagged,replaced them with a set that prior owner had added many leaves to. car sits up high like I like it but above ~35mph the car vibrates & seems to be getting worse. Any sugestions on what degree of tapered shims I should buy/add to get it back to where it was as far as pinion nose up/down? I should have measured the height increase before/after but I would say ~ couple of inches. thank you for your time.

Here's the info you need but you'll have to do the set up yourself. There is no one size fits all cure for this problem. http://www.moparts.org/Tech/Archive/rearsusp/13.html

Thanks Stumpy. I will dig in there & see what I can figure out.