If you go and get a sheet metal gauge you can measure the correct thickness of your metal just be sure if you cut out a piece to file the edge so you can get the right thickness. My 62 C-10 floor is 18 gauge along with my rocker panel and replacement door post.
62Blue
Don


62Blue
62Chevy in progress
You've never been lost until you've been lost at Mach3" Paul F Crichmore (Test Pilot)