Well I heard that those new bugs have a little turbo in them so they didn't need as big of an engine. Smaller engine with a similar power rating should get better mileage.
So if we lower the F150 and have it naked(no grill guard, tool box ect.) with a bed cover, add more gears, chop out any metal parts that are not being directly used, put little narrow tires, the OP's mods, and with a lazy right foot you might be able to get good mileage...down hill.
