My 1954 wagon project

What's up everyone! Just picked up a 54 chevy wagon and am looking for some opinions. Needs a lot of bodywork. Plan on removing the body from frame. A & B posts are rotted through, rockers, body mounts also badly rotted. Typical for a NE car. Frame needs repair before rear end can be installed. Seems like a daunting task to try by myself. Wondering what rust repair I should attempt BEFORE lifting body? Concerned how much body will lose plumb and be out of square? Anyone got advice? Thanks & be kool.
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I'd be inclined to fix the pillars and rockers, then tack some tubular supports inside to stabilize the car. Then pull the body to fix the body mounts and presumably the floor.

 

If the body mounts are badly rotted, the body might already be out of square. Lift it off and block it up straight and level before doing any repair.

 

Yeah kool. Thanks for the replies. You guys are just confirming my thinking. And yes floors are also rotted. I'd thought about doing the rockers first then the floor pans just to have a square frame to start with. Thanks guys!