Some of you are very close to hitting the nail on the head. In the 80's and 90's I was a member of the National Chevy/GMC Truck Association based out of Apopka, Florida, and also the Napco Owners Group (a club for early GM 4x4's). These clubs put out newsletters and a monthly magazine called Pickups and Panels in Print. These publications went into detail about the history of Chevy's and GMC's. Yes indeed, the GMC was the producer of military 6x6's in WW1 and WWII. You will not see an old military 6x6 (or 4x4) that was a Chevy, they were all GMC's. In the late 40's and 50's Chevy's and GMC's were quite different. Most Chevy's during this era were considered lighter duty than thier fellow GMC's. The GMC frames were heavier (stiffer), and the GMC's used Pontiac engines because they usually put out more horsepower than the Chevy's at that time. Also, more of the GMC's had V8's under the hood, where Chevy's usually ran anemic stovebolt 6 cylinders. They were very reliable, but you wouldn't be getting anywhere very fast. This had as much to do with the low gearing in the diffs and the granny low 4speed trannys as it did with the slow revving stovebolt engines. That changed in 1957 when Chevy began using the 265ci V8 in trucks and a couple years later punched it out to 283ci. They also started using some automatic tranny's in trucks at this time (interestingly it was mostly in the GMC's with the big V8's and also the Chevy Cameo which was the predecessor to the El Camino).Over time the differences got smaller and less obvious. From the 1920's to the present they have always had different grills to help distinguish them, but now many of the components are similar. I think it was about the early or mid 1960's when many of the differences started to disappear completely. By the time the first K5 BLazer rolled off the line most of the differences were only cosmetic. Now, I hear that sometimes you can order something on your GMC that you can't get as an option on a Chevy and vice/versa. But you no longer see Pontiac engines in GMC's and I don't think the frames are any different now days.
If any of you are interested in old Chevy or GMC 4x4's visit the Napco Owners Group web site at
www.napco4x4.org. It's very interesting and very educational.
By the way, I am still the proud owner of a 1956 Chevy Napco 4x4 that my father gave me when I was in high school. I've had numerous chances to sell it over the years, but I'm glad I didn't. I just need to quit playing with my K5 so much and finish the restoration of the '56.
