Very good, that is it of course!
The Austin K4 was a truck, so that must be how this special got its name. There is much speculation on the sites where it appears which 6-cylinder Austin engine was installed, whether it was from a Sheerline or indeed from a truck, but I would say its name confirms that it did indeed have a truck engine!
Quite a bargain for $500, although I think it might cost a little more than that today...!
Well done.