1957 chevy convertible vibration

I updated the transmission to a 700R4 in my chevy convertible. It now has a vibration in it. Does anyone know what could be causing it and how I could fix it? The starter bolted to the old transmission so I had to use the thin starter plate betweens the trans and engine for the starter to bolt to. Please help. Thanks, Dave at [email protected] Dexter Mo.

Dave, no one sitting at desk here can diagnose a " vibration" without any definitive description of the how, when and where, agreed?