Can anybody tell me where exactly to find the casting dates on the 283 or 327 block and on the heads of my 65 or 67 chevelle? Thanks, Jim.

For the block, it's on the driver's side shoulder where the upper trans-to-block bolts go. That's on the top of the block just beyond the valve cover between the distributor and brake MC if everything's still together.

For the heads, you have to pull a valve cover.
www.mortec.com (http://www.mortec.com) lists years and casting numbers.