If it was me the transmission would come out and torn apart. Close inspection of the case checking for cracks would also be done. Then a good check of transmission mounts and engine mounts

1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

Livin and lovin life one day at a time