Wikka history on the HZ

[Vombil]

"The 1977 HZ series received minor updates to the exterior, and saw the introduction of what Holden termed "Radial Tuned Suspension" (RTS) on all models. RTS made significant changes to the suspension of the car, greatly improving the handling finesse, while at the same time not compromising ride quality.[14] Modern Motor magazine described the HZ as "a great handler spoiled by the car" in a comparison against the BMW 528i, contrasted as "a great car spoiled by the handling".[15] In this series, the lower-end Belmont was deleted and the Kingswood became the base model for sedans and wagons, with a new model the slightly more upmarket Kingswood SL introduced. Commercial vehicles—the ute, panel van and cab chassis—were not affected by the rationalisation, with the practice of "unbadged" commercial vehicles continuing. During the course of the HZ series, equipment levels were upgraded in 1978 effectively to match improvements in the opposition Ford Falcon range, but the life of the Kingswood looked set to end following Holden's release of the VB Commodore range of sedans and wagons in November 1978. After 1980, Kingswood passenger cars were cancelled—replaced by the downsized Commodore.

The final HZ Sandman, featured a choice of V8 engines only, along with a four-headlight grille and under bumper front spoiler. According to a GMH Price List dated 25 January 1979, a basic HZ Holden panel van was priced at A$6,076, with the Sandman option package an additional A$1,700. The further optional components also included 5.0 litre V8 engine and a limited slip differential. If a buyer selected every Sandman extra, the price would be more than 150 percent of the cost of the basic HZ model. By the end of 1979, the Sandman had largely lost its place in the contemporary Australian youth culture—order figures were down and many of the vehicles were now being sold with the stripes and tailgate logos deleted. The Sandman ute was phased out of production prior to the van, the last of which was manufactured around October 1979."

[HK1837]

Here are the mistakes:

Not all HZ had RTS.
Kingswood SL was the base model for sedan and wagon, Kingswood was a special order delete option on a Kingswood SL.
Commercials weren't unbadged, they had HOLDEN badges on them - this is what they were called. Only the BO6 1-tonner and DL7 Sandmans had no badge.
VB was released much earlier than 11/78.
In 1980 all Passenger Holdens were cancelled, not just Kingswood.

Sandman stuff is closer to being correct.