There's far more then .010 slop on the converter to flex plate attachment. I line bore all my engine blocks and normally run a manual trans. I have a fixture to measure and make sure the tansmission mount is centered on the crankshaft centerline. Not sure how you could set one up with an automatic.... Are you sure the alingnment pins on the block are in good condition, and long enough to come all the way through the bellhousing holes???