Is it just my eyes, or do the pix of those replacement floors not look like a correct 5th gen floor?? Note how the floor is corrugated in the rear... The corrugations on the driver's side front do look correct, however. Perhaps GM changed the design over the years?
to find new sheetmetal (diff gauges, in new flat sheets, usually 3 X 6 ft) check with your local sportman/amateur stock car racers. They always know where to find it at the best price. around here, a 3 X 6 ft sheet of 18 ga. goes for $39.95