63 Dart 383

You've got to REALLY WANT a big block in a early A-body, to deal with all the complications resulting from trying to put a size eleven foot in a size seven shoe.
To try to do it just cause you have a motor and trans available, is a bad idea.
I'd consider posting a trade add here, will swap 383 (and maybe trans) for good 360..... and start from there.
Good Idea.