I have a 1970-vintage Oldsmobile 455 motor for sale. It is a long block, and has 1970 E-Code heads on it, which means it's most likely the 370hp B-Body engine. It is ideal for a rebuild, and appears to be a standard bore block. The short block appears to have been rebuilt at some point, but the heads have not been rebuilt. Here's some pics:
I'm asking $400/BO, and delivery to the Challenge may be possible. Throw me an offer, maybe trades?