Duster full floor pan replacement

Hi, the whole floor on my dad's Duster is pretty bad and will need to be replaced. We like the idea of replacing it with a new AMD full floor pan instead of the individual pieces. However, the car is completely assembled and all the videos I've seen are with the car stripped down. My question is, are we able to do this with the motor and trans in or will the body flex too much with the floor out? Thanks for the help in advance. Here is a pic of the floor at the moment.

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