[*13*]

Every time I've had an over heating issue, I've over thought it. Go with the proper thermostat.
Make sure it is a quality unit.
Make sure your water pump is turning the proper direction (easy to have the wrong one with small fords).
Put your number one piston at tdc & check the mark on your harmonic balancer
Make sure your radiator is free flowing & the proper size.
Make sure your radiator fan is turning properly

A new engine can run a little warm. i would be nervous if mine sat at 210 but, you should see it go down when the thermostat opens, right? A big enough radiator, full of coolant will cool off when the thermostat opens. If you're running a 160Deg, you aren't giving that radiator much time to cool that liquid. You'll likely get it up to temp & the thermostat will not be able to close the system again.