8 3/4 gear set up help

I too use the MW depth tool and it is the right tool for the job. That said several years ago I had I bought a set of 3.55 Motive gears for a Mirada that I installed a 68 B body 8 3/4 in. And I too had a whine at 40-50 when cruising. After several atempts at resetting the pinion/BL, I just gave up and wrote it off to a poor set of gears.