[C10 - C90 Bill]

The '66 and '67's have Thinner Round Directional Lights located on the sides of the Cowl. Sometimes they are hung on the Mirrors like the truck above, but I would really say that was more in '66 than '67. Also the Style and Location of the "GMC 9500" Emblem. The early ones also have the separate "Diesel" Emblem on the side at the front, also like the truck above.

In '68 and '69, the Directional Lights got moved to the Front, were still Round, but a little different Style and somewhat Thicker. I believe the Emblems then got changed to the type that we are more familiar with, moved to the side of the hood, and also the separate "Diesel" Emblem was dropped.

In '70, the Directional Lights went to Square.

As mentioned above, it seems like the Triple Horns were on the early ones only.

Now this is all for Low Hood Trucks.

The Raised Cab was out in '73 or '74 and had many visible differences.

Dan will probably know more about the Raised Cab trucks than I would. But I believe one of the reasons was to have a Larger Radiator in it.

But when I try to determine the year of a truck, I try to take all the details available into consideration, and as mentioned above, once something is changed around, it can be a challenge, lol.

The real way though, if possible, is to check and decode the VIN on it.

Bill