looking to identity 350 chevy casting number 3870010 can not find anywhere!!! Same engine the stamp number passenger side front behind alternator on the block is T51509012 Any help would be appreciated
Casting No. 3970010 = '69 327 from Camaro, '69 327 from trucks and industrial, or '69-'80 (vehicles unlisted). You'll need at least your assembly date (number stamped in front of pass side head, which is No. 4 on the location diagram on this site) to narrow it down, assuming that number has a suffix code.
For example, my casting No. is the same as yours, and my assembly date is F0102CKL. That suffix code "CKL" narrows down my options, and identifies a range of years that I can then cross reference with the casting No. Removing the ones that don't match, I'm left w/ a 350 from '73.