if power top fails to work

I guess a power top like I had on my '64 Dart GT convert can fail for electrical, hydraulic, or mechanical kinds of reasons.

What I would like to know is if it fails can it be moved by hand as if it were a non power top, or is it unmoveable, stuck in place, wherever it is. Bad enough being rained on cause it won't close, but having it fail in mid position also really bad if it can not be moved to full up or down.

Maybe failures are/were rare, but 50 year old stuff is what it is.

Also can a manual top ever be converted to power? Sounds like a big job and not even the frame for the top is the same, they say.