c10 stock floor frame

what size square tubing is everyone using to stock floor there trucks to the rockers. im just tryin to get an idea on what i need to get

Go to fullsizechevy.com. There is a good article on there about how to do one. I'm not sure what year truck you are talking about though. I've seen both 2x3 and 2x4 but I think 2x3 is the most common.