An Express Styleside or Flareside bed is 9' long, only used on 1957/66 F350's.
1961/66 F100/250 4WD's were available with 6 1/2' or 8' Styleside or Flareside beds.
Styleside 4WD: 1961/65 F100/250 4WD, 1966 F250 4WD use the 1957/60 Styleside beds. It's called the "wrong bed" by enthusiasts because the cab lines do not match the bed lines.
There is no such thing as an F100 4WD "High Boy" regardless of what year the F100 is.
The term High Boy (not correct Ford terminology), refers to 1967/76 F250 4WD's and 1977 F250 4WD's assembled before serial number Y20,001.
Some peeps call 1959/65 F250 4WD's High Boys, but that's a matter of conjecture.
There are no production figures available for 1965 F100 4WD's, because Ford combined the 4WD production figures with the 2WD production figures.