Cab corner & rockers are best to be bought, the time you will spend making cab corners is not worth it. the floor you may be able to fab, all depends on how flat it is. I replace a couple of cab corners about a month ago for a friends GMC and only took an hour or so to remove the two cab corners with a grinder & cutoff disk and mig weld them into place and a skim coat of filler over the welds