Will this "275/65R18" fit?

[TommyJoe]

They may have, but you would think the door sticker would have been changed to reflect the change,
and now I have to pull the speedo and see if that was changed to reflect 4 inch smaller tires.

 

[tallsville]

my ex did that to my expy. Brought it home with some smaller f150 rims and tires, that she bought from her dad. Cant remember the exact size but they were 29" tires vs 31" stock. Kept them on until i got my current set up, which was a few years. Luckily i got rid of both.

 

[Spades]

now I have to pull the speedo and see if that was changed to reflect 4 inch smaller tires.

No need to pull the speedo. Just compare it against a GPS. I should point out however that every car ive compared to a GPS usually reads 1-2 mph faster than the GPS readings, so id say allow for a little bit of tolerance before assuming its been altered.

255s were another stock tire options, so maybe they got a deal on the set?

The F150s had the 255 but they i believe they were 255/65-18