Will a Head gasket from 2006 work in a 2003 pontiac

It might but with a part like a head gasket, or any gasket for that matter, you don't want to get a used one. The labor to replace the head gasket on your 2003 model will cost more than the vehicle is worth. I would suggest looking at the 2006 model as a replacement vehicle for the 2003. If the 06 is a good buy, you can always scrap the 03 and get about $250 for it. Hope that helps! Jim