Pull one wire at a time to see if noise go's away.

Unbolt torque convertor to see if its trans.

Make sure no leak at head pipes. Exhuast leak sounds faintly simular.

FWIW
Use snap gauges and mic to check concentricy of rods-n-bearings
Sometimes just need to massage back of bearing halves to get correct tolerance.
Just make sure no scotch brite particles left during assembly. They eat metal.