I did a search and only turned up two posts that even referenced this site. So I wanted to post it for everybody to check out. The site was down for a few months, but now it's back up. I'm hoping it gets enough traffic that the webmaster decides to keep it this time. www.chevytech.com If you are building a sbc and wants specs of any kind that is the site to use. They even have actual pictures of machining marks on the side of the heads to tell the difference. All casting numbers, dimensions of parts, a****st many many other topics. Truely amazing how much info is there. Somebody put a lot of work into that site and it would be ashame not to use it. Go there and click around, you'll be amazed.