[elmariachi]

Possessing test pilot DNA, I'd shim it with some big thick washers, crank the bolts down and have wifey follow you for a quick spin. Probably not the safest move, but operating a Cobra in general is arguably not very safe either. This of course after you try the pinion alignment. I'd be surprised if .4* deviation would induce such a vibration given that you have a tight driveshaft and new driveline components. I guess anything is possible.