Help! Small block 360 has a knocking sound

My money is still on the flex plate.
loosen you torque converter bolts and remove them. make sure that the converter will slide back into the transmission.
should have about 1/4 or more clearance between the flex plate and the converter.

Make sure the car is facing uphill so the converter stays put and START IT UP.
Its only going to take 10 sec of run time to know if it there.