A999 Transmission mated to a 73 340 motor

B&M doesn't balance them ? 10235 is correct for B&M
But not correct for an A904/999. The balance is right, but the larger diameter (so it can use both 10 and 11" convertors in the 727) often rubs in the smaller trans., which is why it specifies 727.
Sometime if you use the 10235 with a 904 it will rub against the starter.
Which brings up a good point- the 10235 could be rubbing, and the scallop makes it feel like a vibration.