Early 360 blocks

Thanks for the replies. I guess I'll start with the earliest I can find.
I have the time to search and not grab the first thing I find. We have
some old yard's around here and looking around is fun.

This will be for my grandson and I just want a good foundation not
largest overbore. I do have access to an industrial sonic tester so
I can know what I have. To bad you can't check before you buy.

Danny