Patrick,
I know it's tempting, but don't throw them over the edge... Chev's of the '40's is currently buying Rochester B cores for up to $75. Here's the form:
Chev's Core Form.
I sent in three that were pretty much basket cases, and got full value on one, and half the max amount on two that were missing parts. Not a bad deal for what I considered paperweights.
Cheers!
Doug