I think the B manifolds fit the 67-up “later A”. I’ve done that before. I do not believe they will work in the early a although my experiments were with the RB it wasn’t even close where that shorter deck provided the room.
The 68-69 B body HP manifolds do fit the early A with with a low deck with the steering column body trimmed to the firewall and floor shift. There was a guy over on Big Block Dart that did one and it fit good. It was a blue early A. He had some good pictures, too.