I would like to see a "steel construction" thread. I construct a few a year and have also notice in my area, alot of people are starting to make houses out of pole-barns or weld-up metal buildings. I am also in the process of doing this.
I'd suggest you try
Roshmetal company.
Check out their web site for details on their Metalworking program.
They have a pretty wide appetite and I'm thinking they can likely do that for you. Probably the most comprehensive site for a metal building company, you can price every little option out, looks like no surprises. You can even look at an assembly manual online.
Good Luck!