[Keithc8]

We machine the block for the one piece rear main seal after we do the line honing so it is on the exact line hone center and with the crank center. We have very few rear main seal leaks on the 351W blocks or the after market Dart blocks which also use the one piece rear main seal. Just make sure you check everything because all leaks seem to end up at the rear of the engine. Good luck, Keith