You pull the 4 thrubolts out,remove the fan & pulley,slide the front housing up the shaft until it clears enough to rotate.Then reverse to reassemble.By looking at the back with the threaded ear at 12 o'clock,line up the plug area to that,most of our Buicks are at 12 o'clock There is no other physical difference besides single or double pulley on stock alternator.
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