Confirmed: Wikepedia says:
"Ford never adopted the straight-8, using V8 engines in their entry-level cars and V8 or V12 engines in their Lincoln luxury cars from the 1930s on."
However, I googled "Ford straight 8" and found this:
How About A Straight-Eight-Powered Ford Tempo? T-Drive!
Admittedly not a production engine but interesting anyway.