Pinion angle question.

LEAVE IT ALONE and run it. LOL

pinion 2* down gives you a -4.5 pinion angle. A little higher than ideal for a streeter, but doable.

If it's vibrating on decel, that's because the pinion will dive further negative stressing the u-joints, so maybe roll it up 1 to 1.5* and see if the vibration reduces or goes away.
Yea it definitely has a pretty good vibration on decel and when I have the throttle in just enough so the rpm aren’t dropping but the engine isn’t pulling it also vibrates quite a bit. I’ll buy a pack of 1* shims and mess around with it and see what I can mess up. :D