I went back and read your post again and the car now has another engine in it and it still vibrates????? I`m stumped too, vibrates sitting still and you`ve changed out the engine, flex plate, torque converter??? The 360 is likely to be externally balanced and will need the appropriate torque converter. Do you have good motor mounts? Are they steel or rubber?
Yes, I've changed everything to 360 stuff. TCI told me all of their converters are neutral and the balance is made up in the flexplate, which I have from B&M. The mounts are rubber spool type and are in good shape