I'm not too sure what the stock number is for the plugs but they are going to be a Platinum Motorcraft plug, that much I know for sure. As for whats a good plug to use for a n/a application, most use copper spark plugs and just change them out every year. I run Motorcraft awsf-c12's. They are copper and are two steps colder than stock. If you want stock heat range, I'm not sure what the Motorcraft number is but Autolite makes a 764 series copper plug which will work. Its copper and stock heat range as well. You could also use Iridium plugs which will are more conductive than platinum but will last far longer than copper. However, they are really expensive.