I think I found my vibration problem

B+M makes 2 flexplates for a 440, the one pictured above has a large cutout-it is for a cast crank and a converter without weights. B+M also has a fully round heavyduty neutral balanced flexplate for a 440-with a cast crank and weights on the converter. I would rotate the engine a full turn and look for weights and the flexplate cutout area. IF you have the cutout B+M flexplate-any converter guy should know you do not need weights on the converter.