I've seen a lot of old Chevy pickups with removable tops. I've seen a few articles on it in Truckin magazine. None of them left the doors uncut. If it's too much work don't do it. It's easy to make the doors open with the windows up. If you gave it a lot of thought and still can't figure that out then the job is beyond your abilities. The back should be cut at the beltline. Even with the top of the doors. Not even with the bed. The 41 Chevy bed is about a foot below the beltline.
AL