The structural integrity can be maintained if you replace one piece of tub at a time.   Screwing a board between the tailgate opening is helpful.  I have seen people install a brace above…and toward the front of the wheel houses too.  You may consider more bracing if you plan to do the cargo floor.

I started by replacing damaged pieces on the sides.  Once complete here, I flipped the tub on edge and replaced one portion of the floor at a time.





I did re-install the tub a few times to make sure I was keeping everything in alignment.
 
There are clearly other ways to do this.  With limited space and skill set, this did work well for me.

Hawk 

Cory wrote on 07/13/16 at 16:10:25:


It couldn't be much worse than this...right?   





The 'piece meal' approach helped me mentally.  I was a bit overwhelmed by it too.  I had never tried anything like this.  Eventually, I ran out of rotten stuff to replace.  My confidence grew with every move.  Yours will too.

The photo above was my second attempt at restoring a tub.  That one was fun.

Hawk

Thanks!  Hawk, mine isn't *quite* that bad.  But I'm trying to avoid having it look like that in the process.  I appreciate the words of encouragement.  I'll post pics when I dive in!

And, Mark.  I was looking for an excuse to add more firepower to the tool arsenal!

I did use wood to hold sides and keep straight sides or use the wood to help straighten as I went



I don't have things orderly but this part of my pic's have a lot of the body pieces I worked on

http://www.surfacezero.com/g503/showgallery.php?ppuser=689&cat=500&page=68