This is indeed a rare truck.

In 1956 American Motors and General Motors entered into an agreement where AM would use GM pickup runningboard stockpiles and in turn GM would receive AM's collection of the now defunct Hudson Italia (1955 Hudson SuperJet) parts stockpile.

Badged as the 1958 GMC SuperJet 100, this short wheelbase truck package (pictured in the Ebay Ad.) featured oversized tires, a -factory- Barden bumper, a medium duty truck door mirror, and the special Hot-fire™ 235 engine package which included yellow spark plug wires.

You could get your GMC Superjet™ in any color that you liked -- as long as it was the factory "Avocado Hurl Green". It came with a low-profile, -sleeperesque- trim package where all but the GMC and SuperJet logos were "whited-out."

Another interesting feature that only appeared on this model was the special SuperStayShut™ glove box latch system that kept the glove box door sealed tight over rough terrain.

Missing from the truck advertised is the ultra-rare "bird cage" (not to be confused with "bird catcher") air cleaner that was part of the Hot-fire™ package. Included is what appears to be the original white sheet seat cover.

Unfortunately, sales were anything but brisk. GM only sold three of these trucks, one of which now resides in Stink Butt, South Dakota. The other two are believed to be submerged in the Duwamish River along with one 1965 Chevrolet C20 and a 1987 Yugo GV.

[img]http://www.norcalspeedshop.com/_offsite_images/bodsuperjet.jpg[/img]

[EDIT:] Stink Butt should read "Mud Butte."

I neglected to mention something:
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...the external oil feed to the head...
This too was part of the Hot-fire™ package. A special thanks to Tony P for pointing this out. Thanks Tony P!