There's several types of aluminum...aircraft type, which is usually the strongest, T7 which is just a code and tells you the strength of aluminum and class. I should know...I work with aluminum aerospace all the time. T6, T5, ect...I think as the number gets smaller, the softer the aluminum. Toolmaker can correct me if he wants, but as far as anything special he uses, only he would know(well duh!). Not sure what makes billet aluminum tho...
'97 4 dr. Tahoe
Polk Audio MM6501
Wolfram amps 3000.1, 125.4 coming soon
2 Sundown Audio X 15's Tuned @ 30Hz.
Interstate battery/Royal Excelene/KnuKoncepts Kolossus wiring