I just ordered a WebSteel 30' x 48' x 14' eve kit. The steel columns are 12' on center. Three of the four bays will have 10' wide by 12' tall doors. The trusses are all steel. There are 2 x 6 girts and 2 x 8 purlins douglas fir so that insulation and dry-wall can be put up. I bought one of their "internet" specials... a standard package... I didn't need any custom features. I plan to put a four-post lift in one of the bays (that's why I went to the 14' eves).They will design custom buildings. My package runs about $7300. I will do the install over a monolithic concrete foundation. I helped a friend put one up last summer and was impressed. See the options at
http://www.websteel.com/
No affiliation with Websteel.