I was installing my Gibson exhaust system the other day and noticed that my drive shaft looked to be aluminum. Is this standard or was it some type of option?

 

Standard equipment. Be sure if You ever replace the u-joints, to use Spicer. Spicer makes a u-joint that has a coating that resists oxidation of dis-similiar metals. Conventional u-joints & conventional Spicer u-joints do not have the protective coating.