After 74/75 model changeover, the two choices for a 1/2 ton were an 8 1/4 or a 9 1/4. There wasn't much rhyme or reason for which one ended up in which truck. I've seen a fair share of what was suppose to be heavy duty trucks with the 8 1/4, and light duty trucks sporting a 9 1/4. I suspect a great deal of them depended on what was checked on the order form, or what happened to be around at the assembly line. Gene