Ive got a 30 - 31 chevy truck and every piece of wood that was rotten or broke on the floor I replaced with 1x1 tubing and plywood floor, the cab I put angle iron and bolted it threw the wood , my tin is nailed to the wood , thats why I kept as much wood as I could, my doors still have the wood frame on them and you see the nails all around it
on the 30lSH we used one by one tubing for bracing the structure to replace the wood, it worked very well. the car has a solid feel driving her, even at 9O+.
If you don't have a bender there was a guy on ebay that was selling elbows but I looked and didnt find them. Here are some more that can sure speed up the the process. http://www.quickfab.ca/