Man My dad had an El Camino with a 396, would lay two strips of rubber shifting into second at 55mph.

Have you ever filled a torqueconveter? It takes 3 qts and it is a slow process. A dry trans and converter takes 12 qts of fluid. I don't know if it is a good idea to run the engine to fill the tq. Ask who ever is warrantying the transmission. My guy spicificaly told me to fill the converter first.