Yea...ebay sells adapters. You'll need a 5x4.5"(Ranger) to 5x5"(F150).
And they are 18x8s......have fun spending LOTS of money on tires.
But ya know...you could always go with Mustang Cobra rims....they look AWESOME!!!! Plus, they still are SVT rims and look similar to the Lightning rims, and Mustangs are 5x4.5" bolt pattern, just like our Rangers. D. has a set on his truck, along with some others on here.