The term “Highboy” has been used to refer to the 1967-1977.5 Ford F-250 4X4, although 'Highboy' wasn't actually a Ford term. The early 4X4 pickups were conversions of a 2WD chassis. ... The end result was a higher cargo loading height verses that of the 2WD F-250, and a higher center of gravity.

What makes it a highboy?

Highboy” is an unofficial slang term for pre-77.5 F250 4x4s. They do in fact have a narrower frame. The front bumper mounts on special brackets that adapt the narrow frame to the wider hole spacing on the bumper. There is a bar connecting the bottom front of the frame rails.

When did Ford make the highboy?

F-250 Highboy (1973-1977)

1973-1975 F-250 Ranger 4x4. Note location of "divorced" transfer case below cab.