PP's have different pistons and rings than non-PP. The reason is that these are police interceptor motors, designed to idle for a half hour then go to wide open throttle indefinitely. Ceramic is one of the premium materials. Can't divulge any more.
If you have a pp, you will have different limits than a non PP. Also, since earlier this year, all blocks now have fine thread main bearing caps, much stronger, though it will only apply to Flex, F150 and Explorer sport. Still something to consider during a rebuild.