I have an 11B '66 (Norwood) convertible with casting dates of H6 intake, heads, and block. I don't have documentation such as protect o plate, build sheet, or original invoice, but the engine is a 10/22/66 MM assembly stamping which is a L30 with powerglide.
I also have a friend who's grandmother just left him her 1967 Impala (purchased new and built in February of '67), four door, no power, no air, L30 (327-275) with powerglide. It has casting numbers of H-16-6 block, H-16-6 heads, and H-16-6 manifold, I know........ unbelievable!! (for a March 1967 Impala) The block assembly stamping is so rusted that it's non retrievable - believe me, we have TRIED.
The difference between a hobby and insanity is .0000001"