As many original GM parts as possible but not so strict on date codes, etc. How many original '68 YT blocks are out there available? If you can find them, let me know, I need two of them. I would be a purist if I could, but neither of my cars was in good enough shape to be able to do so. But with that said, I'm not putting a 428 in a first gen that was originally a 400 from the factory or a 326 for that matter.