4spd swap problem

I recently replaced my 727 auto for a A833 4spd hated driving the auto. So everything works as it should. But I have a vibration that was never there before. I rebuilt the transmission not my first time. New driveshaft custom made with new yoke and joints. The issue happens when I I drive or even sitting in driveway not moving just rev it up. It has a 360 that I had a b&m flex plate no vibration. The flywheel was balanced with clutch cover bolted to it. My question is internal vs external balance did I do something wrong Or am I going in the wrong direction here.