Below is a link for the boxes that are currently on sale if anyone is interested.
https://slickdeals.net/f/11446475-husky-extra-deep-46-in-9-drawer-mobile-workbench-248-home-depot-starts-4-5
I didn't really think of the corrosive issue, after the wood dries out I will either paint or stain. I may end up putting some type of barrier where the toolbox comes in contact with the wood. I'm going to do a little research on that.
I actually have a 4x4 supporting the middle joist the help...
After several months of contemplating I decided to go with the Husky boxes after the were redesigned. The boxes were on sale, measuring 48w" x 26d" with double rollers on the larger drawers, and pre-cut liners(also came with surge protectors flush mounted which I will use in my top). Found them...