3" level

I'm gonna buy this leveling kit hopefully today. http://www.topguncustomz.com/Store/Gen2ProdDisplay.php?iview=244941979 Could I stack two 1.5 inch spacers on top of each other to give it a total of 3" in the front? I want to order two 1.5" kits. Would I need new shocks with the level? 1.5" or 3"?