I have a 73 340 block, getting engine vibration at about 1500 rpms, not sure if the crank is cast or has been changed to forged. It has what appears to be a 360 external balance dampner on it, It is connected to a neutral 904 converter. Question is will the 360 ext balanced dampner work on the 340? If it is a cast crank, DO I need both the correct dampner and weighted converter (or flexplate),or just the dampner with the neutral converter, in order to balance the motor? Not sure exactly what I have got a hold of, everything I have touched on this motor has been cobbled together so far, so not really sure I can trust anything on the ext of the motor to be correct. Any help will be greatly appreciated