well i figured it out. After hours of research i finally dropped my trans to check for correct flexplate install. Sure enough, the flexplate was a couple holes off. The scat crank did not have a dowel pin and i just slapped on the flexplate. So, I learned, on a externally balanced 383 the counter weights on the flexplate and harmonic balancer need to be aligned properly. If not, you WILL get a vibration.
Live and learn, my next engine will be evan better. This is the first engine I have built, still cant believe it runs lol