Greetings and welcome. You've already got two of the top hands on board with Bubba and Harold. I think the line between "shell off" and other methods is fluid and depends on a combination of many factors. I have never done a total lift the shell and slide the frame out job. If significant frame repair or modification is in store this may be the way to go. I like to do what I call "floating" the frame. Interior is completely stripped, bellypan off, trailer in a solid, level surface (relatively) and I get it 24" off the ground on 6 ton jack stands. Then I work in sections or ends of the trailer so that even though the shell is completely disconnected from the frame with blocks around the edge its just an inch or so above the frame. This may not work on all years and models but I think is possible from the 50's to at least
1968. Later F style channel makes this much harder. Taking the whell wells out also really helps. I've done several this way with the total floor on my '68 taking just a three day weekend and all full sheets. Needless to say there was lots of prep leading up to this and I needed no frame work. So much to think about, read threads and ask questions.
Good luck, Mark D