Get the tuning guide and try it. If it drives better, great, and if not you change it back. If it is better, go farther and change it until it complains then back up a bit. Try rods first then jets. Changing rods is 5 minutes and jets is only a 20 minute job.
Nobody can tell you what it's going to like best from here.
As for the vibration, I've been reading that overdrives create some peculiar vibration issues. I'm ready to start playing with pinion angle to see if it helps. A recent HRM article was about a car modified by the GM Desert Proving Grounds. They were running 8 degrees POS pinion angle just to combat OD vibration. It sounds extreme, and may be a misprint, but I have read elsewhere that changing pinion angle may help. Wedge plates are an easy "try it."
