I have one of the blocks you want, and it is in long block form. It is a pretty clean 400 with a late 71 Casting date. I have photos to prove it. I also have a 361 from 1963 that is locked, but it will give some parts over to the 400 if need be. Buy the pair for 400, or buy just the 400 for that, since it is the desirable block. Send me a message if you are interested.