No HX-HZ Sandman aren't a model. They were intended to be viewed as a separate stand alone vehicle like a HX LE, or a HQ Monaro GTS sedan. The actual by the book model codes on these examples are not what the vehicles were ever intended to be: HX Holden ute, HX GTS coupe, HQ V8 Kingswood sedan. You have to look further than model codes on any of these to know what you have, in all three cases it is or can be the trim code. Yes the LE is easy as there was no other HX coupes, but if the LE had been built when the bodies were assembled in 1975 it would have been a HJ LE coupe and then you'd be in the same situation as others ie check the trim code.