I believe I have a 350 I'll know more once I finish getting it out of my c10. The date stamp is pretty much gone but here's what I got. It's 3970010 block, not sure if it's a 2 or 4 bolt yet. Just trying to figure out what it was originally in. V10210NU 10C125026 The heads are 64cc 3927186, not sure if they're original to the block.