The Whirlwind is an Imperial artillery support vehicle based upon the Standard Template Construct (STC) Rhino armoured personnel carrier (APC) chassis that is now primarily used by the Space Marine Chapters of the Adeptus Astartes.
This is the kit version of the original Whirlwind artillery vehicle, based on the original Rhino kit. It was on display at Warhammer World.
It comprised a plastic Rhino kit and metal components.
The original Whirlwind was a conversion using a slottabase and plasticard for the rocket launcher. This was published in the September 1989 issues of White Dwarf, #117.
The Rhino APC is perhaps the most common vehicle in the Imperium. As a basic design in the STC system, it exists in thousands of variants, each of which can be considered a vehicle in its own right. Each different design is much more than a simple conversion of the standard Rhino; every one fulfills a different role, and is impossible to better. The Whirlwind is just one of these designs.
Here are the instructions, just in case you want to build your own.
I prefer this original conversion to the metal one shown at the top of the article.