You need to have the crank checked for runout and the block rechecked on the main alignment. Is it worse on the center mains? If so, I would definately say something is not straight. I actually juste went through a main bearing failure, and mine was due to the machine shop not properly cleaning and brushing the oil passages. I specifically ask for that, but they did not do it. The next shop I took it do did, and they found rust and dirt in oil passages.
Just a thought,
Chris