new 6.7 for sure... its got all its history in front of it still..

while the old Navistar 6.4 will soon be largely ignored by your local Dealer.. pretty sure everyone at Ford will be happy to see those Navi' engines disappear..

even thou teh used truck is a Lariat, i'd still go with the newer tech in the 2011, adn the XLT still has lots of nice features.