I understand the shipping concern. But if the material price is right, the cost with shipping is still lower. I've used Aircraft Spruce and Specialty Co.
for 6061T6 aluminum several times, as recently as last week. The prices for the sheets is lower than anywhere else I've found on-line, and way lower than anywhere I could buy locally. They charged $14.26 to ship 3 sheets of .040x24x48. They ship from Atlanta, so pretty reasonable at this end of the country. Service is also amazing. Ordered Oct 8, was on my porch on Oct 10.
Edit: Two others beat me to it! At least above you have a specific example.
Build 1: Mk3 #5125. Start: 10/31/2009. New build. 306, AFR 165s, QF SS-650 carb, T5, PB, 4-link, Gas-N pipes. Red/white club, legal 09/28/2011. http://s867.beta.photobucket.com/use...Build/Finished
Build 2: Mk4 #7750. Start: 09/09/2012. New build. DART 347 stroker, Levy 5-link, Wilwood brakes, PS. Color? Who knows.
Build thread: http://www.ffcars.com/forums/17-fact...ss-update.html