There are many threads here on the "Highboy".
You can find many of them with the search function.

A few threads are linked below:
https://www.ford-trucks.com/forums/9...mpilation.html
Torque, how 'bout a highboy sticky? - Ford Truck Enthusiasts Forums
high boys - Ford Truck Enthusiasts Forums
What makes a Highboy? - Ford Truck Enthusiasts Forums

The basic definition seems to be:
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A Hiboy is a Ford truck that came from the factory as having the following:
- Built from 1967 thru 1977.5.
- F-250.
- 4x4.
- Divorced transfer case.

Trucks that are NOT considered a Hiboy are:
- Any truck built after mid-1977. It goes by Consecutive Build Number in the VIN# anything built starting Y80001 is a 77 1/2. **
- Anything other than an F-250.

There will always be a couple very oddball exceptions but, for the most part, this is it.

Front axle choices in the Hiboy were either the 8 lug Dana 44 or the old style low-slung pinion Dana 60 (commonly referred to as the Dana 50). Engine choices were either the 6 cylinder or 360 2 bbl. Steering was either manual or power ram assist.

-Basic definition provided by user: BigBuddy

** VIN information provided by Dennis AKA Mil1ion.
===================================

It has been pointed out that the 300, 351M, and 400 were the engines available in the 77 model year.