If your Ad doesn't get a suitable response here, you could try the following contact info. They might be interested in the 312 block & cranks etc.
John Mummert Y-Block, (a machine shop) 14368 Olde Hwy 80, suite C, El Cajon CA @ 619 596- 0312.. (they're busy people, have your info organized). Or e- mail Henaults Enterprises in La Grange CA @
henaults@jps.net & @ 209-852-2476 (specialises in Y-Blk parts)
Paul