Most crate engines are 80ís or 90ís ish blocks. I talked with several of the crate builders and they donít use the older blocks because they are harder to find. So using a crate motor will tie you to all kinds of emission equipment. Some of it not good.
I looked hard and long for my 69 block and found one in New London. Watch Craigís list and the auto journals ads for the older blocks, as they do show up. Iím super happy with my motor and itís state required PCV valve. BTW ..... Iím running a Fitech fuel injection system on my 69 block and it runs strong. If you can find a pre 71 block, itís definitely the way to go.
Happy hunting and good luck with your search.
By the way.... that guy in New London had several pre 71 302 blocks.